When sitting on the world select screen for a few seconds or scrolling down, the game crashes.
I'm using the 1.4.2 version of the mod for 1.20.4.

Unfortunately I can't fix it without the crash report, I've never had this problem before, even scrolling with multiple worlds in the screen.

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 2024-03-01 16:10:46
Description: Rendering screen

java.lang.NullPointerException: Cannot invoke "net.minecraft.class_5315.method_29026()" because "this.field_25023" is null
at net.minecraft.class_34.method_38496(class_34.java:136)
at wily.legacy.client.screen.SaveSelectionList$2.method_48579(SaveSelectionList.java:240)
at net.minecraft.class_339.method_25394(class_339.java:66)
at net.minecraft.class_437.method_25394(class_437.java:121)
at net.minecraft.class_437.method_47413(class_437.java:110)
at net.minecraft.class_757.mixinextras$bridge$method_47413$191(class_757.java)
at net.minecraft.class_757.wrapOperation$bck000$fabric-screen-api-v1$onRenderScreen(class_757.java:2611)
at net.minecraft.class_757.method_3192(class_757.java:931)
at net.minecraft.class_310.method_1523(class_310.java:1327)
at net.minecraft.class_310.method_1514(class_310.java:888)
at net.minecraft.client.main.Main.main(Main.java:265)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Render thread
Stacktrace:
at net.minecraft.class_34.method_38496(class_34.java:136)
at wily.legacy.client.screen.SaveSelectionList$2.method_48579(SaveSelectionList.java:240)
at net.minecraft.class_339.method_25394(class_339.java:66)
at net.minecraft.class_437.method_25394(class_437.java:121)
at net.minecraft.class_437.method_47413(class_437.java:110)
at net.minecraft.class_757.mixinextras$bridge$method_47413$191(class_757.java)
at net.minecraft.class_757.wrapOperation$bck000$fabric-screen-api-v1$onRenderScreen(class_757.java:2611)

-- Screen render details --
Details:
Screen name: wily.legacy.client.screen.PlayGameScreen
Mouse location: Scaled: (325, 190). Absolute: (651.000000, 381.000000)
Screen size: Scaled: (640, 360). Absolute: (1280, 720). Scale factor of 2.000000
Stacktrace:
at net.minecraft.class_757.method_3192(class_757.java:931)
at net.minecraft.class_310.method_1523(class_310.java:1327)
at net.minecraft.class_310.method_1514(class_310.java:888)
at net.minecraft.client.main.Main.main(Main.java:265)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)

-- Uptime --
Details:
JVM uptime: 2150.343s
Wall uptime: 2134.256s
High-res time: 2131.312s
Client ticks: 42000 ticks / 2100.000s
Stacktrace:
at net.minecraft.class_310.method_1587(class_310.java:2564)
at net.minecraft.class_310.method_54580(class_310.java:995)
at net.minecraft.class_310.method_1514(class_310.java:908)
at net.minecraft.client.main.Main.main(Main.java:265)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)

-- Last reload --
Details:
Reload number: 15
Reload reason: manual
Finished: Yes
Packs: vanilla, fabric, custom-fog, disable_custom_worlds_advice, dynamic_fps, fabric-api, fabric-api-base, fabric-api-lookup-api-v1, fabric-biome-api-v1, fabric-block-api-v1, fabric-block-view-api-v2, fabric-blockrenderlayer-v1, fabric-client-tags-api-v1, fabric-command-api-v1, fabric-command-api-v2, fabric-commands-v0, fabric-containers-v0, fabric-content-registries-v0, fabric-convention-tags-v1, fabric-crash-report-info-v1, fabric-data-attachment-api-v1, fabric-data-generation-api-v1, fabric-dimensions-v1, fabric-entity-events-v1, fabric-events-interaction-v0, fabric-events-lifecycle-v0, fabric-game-rule-api-v1, fabric-item-api-v1, fabric-item-group-api-v1, fabric-key-binding-api-v1, fabric-keybindings-v0, fabric-lifecycle-events-v1, fabric-loot-api-v2, fabric-message-api-v1, fabric-mining-level-api-v1, fabric-model-loading-api-v1, fabric-models-v0, fabric-networking-api-v1, fabric-object-builder-api-v1, fabric-particles-v1, fabric-recipe-api-v1, fabric-registry-sync-v0, fabric-renderer-api-v1, fabric-renderer-indigo, fabric-renderer-registries-v1, fabric-rendering-data-attachment-v1, fabric-rendering-fluids-v1, fabric-rendering-v0, fabric-rendering-v1, fabric-resource-conditions-api-v1, fabric-resource-loader-v0, fabric-screen-api-v1, fabric-screen-handler-api-v1, fabric-sound-api-v1, fabric-transfer-api-v1, fabric-transitive-access-wideners-v1, fabricloader, immediatelyfast, infinite-music, keepthatmusic, krypton, lazydfu, legacy, lithium, minecart-turning, modmenu, taxfreelevels, walk-jog-run, yet_another_config_lib_v3, file/ClassicCraft, legacy:legacy_waters_resourcepacks/legacy_waters

-- System Details --
Details:
Minecraft Version: 1.20.4
Minecraft Version ID: 1.20.4
Operating System: Windows 10 (amd64) version 10.0
Java Version: 17.0.8, Microsoft
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Microsoft
Memory: 1379314408 bytes (1315 MiB) / 2013265920 bytes (1920 MiB) up to 2147483648 bytes (2048 MiB)
CPUs: 6
Processor Vendor: GenuineIntel
Processor Name: Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz
Identifier: Intel64 Family 6 Model 158 Stepping 10
Microarchitecture: Coffee Lake
Frequency (GHz): 2.81
Number of physical packages: 1
Number of physical CPUs: 6
Number of logical CPUs: 6
Graphics card #0 name: AMD Radeon (TM) RX 580
Graphics card #0 vendor: Advanced Micro Devices, Inc. (0x1002)
Graphics card #0 VRAM (MB): 4095.00
Graphics card #0 deviceId: 0x67df
Graphics card #0 versionInfo: DriverVersion=30.0.13023.4001
Graphics card #1 name: Intel(R) UHD Graphics 630
Graphics card #1 vendor: Intel Corporation (0x8086)
Graphics card #1 VRAM (MB): 1024.00
Graphics card #1 deviceId: 0x3e92
Graphics card #1 versionInfo: DriverVersion=27.20.100.8854
Memory slot #0 capacity (MB): 8192.00
Memory slot #0 clockSpeed (GHz): 2.67
Memory slot #0 type: DDR4
Virtual memory max (MB): 15555.87
Virtual memory used (MB): 12833.84
Swap memory total (MB): 7552.95
Swap memory used (MB): 2102.25
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Fabric Mods:
architectury: Architectury 11.1.13
collective: Collective 7.36
custom-fog: Custom Fog 2.2.0-1.20.3
disable_custom_worlds_advice: Disable Custom Worlds Advice 5.0
dynamic_fps: Dynamic FPS 3.4.2
fabric-api: Fabric API 0.96.4+1.20.4
fabric-api-base: Fabric API Base 0.4.36+78d798af4f
fabric-api-lookup-api-v1: Fabric API Lookup API (v1) 1.6.49+82b1bb3e4f
fabric-biome-api-v1: Fabric Biome API (v1) 13.0.16+78d798af4f
fabric-block-api-v1: Fabric Block API (v1) 1.0.16+3e2216cb4f
fabric-block-view-api-v2: Fabric BlockView API (v2) 1.0.4+78d798af4f
fabric-blockrenderlayer-v1: Fabric BlockRenderLayer Registration (v1) 1.1.46+78d798af4f
fabric-client-tags-api-v1: Fabric Client Tags 1.1.7+78d798af4f
fabric-command-api-v1: Fabric Command API (v1) 1.2.41+f71b366f4f
fabric-command-api-v2: Fabric Command API (v2) 2.2.20+78d798af4f
fabric-commands-v0: Fabric Commands (v0) 0.2.58+df3654b34f
fabric-containers-v0: Fabric Containers (v0) 0.1.86+df3654b34f
fabric-content-registries-v0: Fabric Content Registries (v0) 5.0.14+78d798af4f
fabric-convention-tags-v1: Fabric Convention Tags 1.5.10+78d798af4f
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.2.23+78d798af4f
fabric-data-attachment-api-v1: Fabric Data Attachment API (v1) 1.1.3+b90db5744f
fabric-data-generation-api-v1: Fabric Data Generation API (v1) 13.2.3+5c0133444f
fabric-dimensions-v1: Fabric Dimensions API (v1) 2.1.61+78d798af4f
fabric-entity-events-v1: Fabric Entity Events (v1) 1.6.1+09fc25014f
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.7.1+389931eb4f
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.2.74+df3654b34f
fabric-game-rule-api-v1: Fabric Game Rule API (v1) 1.0.46+78d798af4f
fabric-item-api-v1: Fabric Item API (v1) 2.2.0+d6f2b0844f
fabric-item-group-api-v1: Fabric Item Group API (v1) 4.0.25+58f8c0124f
fabric-key-binding-api-v1: Fabric Key Binding API (v1) 1.0.41+78d798af4f
fabric-keybindings-v0: Fabric Key Bindings (v0) 0.2.39+df3654b34f
fabric-lifecycle-events-v1: Fabric Lifecycle Events (v1) 2.3.0+a67ffb5d4f
fabric-loot-api-v2: Fabric Loot API (v2) 2.1.8+78d798af4f
fabric-message-api-v1: Fabric Message API (v1) 6.0.5+78d798af4f
fabric-mining-level-api-v1: Fabric Mining Level API (v1) 2.1.64+78d798af4f
fabric-model-loading-api-v1: Fabric Model Loading API (v1) 1.0.8+78d798af4f
fabric-models-v0: Fabric Models (v0) 0.4.7+9386d8a74f
fabric-networking-api-v1: Fabric Networking API (v1) 3.1.7+2e5ac5484f
fabric-object-builder-api-v1: Fabric Object Builder API (v1) 13.0.13+080016e44f
fabric-particles-v1: Fabric Particles (v1) 1.1.7+78d798af4f
fabric-recipe-api-v1: Fabric Recipe API (v1) 2.0.20+78d798af4f
fabric-registry-sync-v0: Fabric Registry Sync (v0) 4.0.19+58f8c0124f
fabric-renderer-api-v1: Fabric Renderer API (v1) 3.2.4+78d798af4f
fabric-renderer-indigo: Fabric Renderer - Indigo 1.5.4+78d798af4f
fabric-renderer-registries-v1: Fabric Renderer Registries (v1) 3.2.53+df3654b34f
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.3.42+73761d2e4f
fabric-rendering-fluids-v1: Fabric Rendering Fluids (v1) 3.1.1+e761c6694f
fabric-rendering-v0: Fabric Rendering (v0) 1.1.56+df3654b34f
fabric-rendering-v1: Fabric Rendering (v1) 3.2.0+6fd945a04f
fabric-resource-conditions-api-v1: Fabric Resource Conditions API (v1) 2.3.14+78d798af4f
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.11.19+58f8c0124f
fabric-screen-api-v1: Fabric Screen API (v1) 2.0.17+78d798af4f
fabric-screen-handler-api-v1: Fabric Screen Handler API (v1) 1.3.55+78d798af4f
fabric-sound-api-v1: Fabric Sound API (v1) 1.0.17+78d798af4f
fabric-transfer-api-v1: Fabric Transfer API (v1) 4.0.11+e84342304f
fabric-transitive-access-wideners-v1: Fabric Transitive Access Wideners (v1) 5.0.14+78d798af4f
fabricloader: Fabric Loader 0.15.7
mixinextras: MixinExtras 0.3.5
fastminecart: Fast Minecart 1.0.0
ferritecore: FerriteCore 6.0.3
giantspawn: Giant Spawn 5.0
immediatelyfast: ImmediatelyFast 1.2.10+1.20.4
net_lenni0451_reflect: Reflect 1.3.2
infinite-music: Infinite Music 0.3.1
java: OpenJDK 64-Bit Server VM 17
keepthatmusic: Keep That Music 0.0.5
krypton: Krypton 0.2.6
com_velocitypowered_velocity-native: velocity-native 3.2.0-SNAPSHOT
ksyxis: Ksyxis 1.2.2
lazydfu: LazyDFU 0.1.3
legacy: Legacy4J 1.4.3b
lithium: Lithium 0.12.1
minecart-turning: Minecart Turning 1.0.0+1.20-1.20.4
minecraft: Minecraft 1.20.4
modmenu: Mod Menu 9.0.0
mr_hybrid_beta: Cascades (Hybrid Beta) 1.0.2
naturallychargedcreepers: Naturally Charged Creepers 3.4
skeletonhorsespawn: Skeleton Horse Spawn 3.8
taxfreelevels: Tax Free Levels 1.3.9
walk-jog-run: Walk, Jog, Run 1.0.2+1.20.3
yet_another_config_lib_v3: YetAnotherConfigLib 3.3.2+1.20.4
com_twelvemonkeys_common_common-image: common-image 3.10.0
com_twelvemonkeys_common_common-io: common-io 3.10.0
com_twelvemonkeys_common_common-lang: common-lang 3.10.0
com_twelvemonkeys_imageio_imageio-core: imageio-core 3.10.0
com_twelvemonkeys_imageio_imageio-metadata: imageio-metadata 3.10.0
com_twelvemonkeys_imageio_imageio-webp: imageio-webp 3.10.0
org_quiltmc_parsers_gson: gson 0.2.1
org_quiltmc_parsers_json: json 0.2.1
zombiehorsespawn: Zombie Horse Spawn 4.8
Launched Version: fabric-loader-0.15.7-1.20.4
Launcher name: minecraft-launcher
Backend library: LWJGL version 3.3.2-snapshot
Backend API: AMD Radeon (TM) RX 580 GL version 3.2.14761 Core Profile Forward-Compatible Context 21.30.23.04 30.0.13023.4001, ATI Technologies Inc.
Window size: 1280x720
GL Caps: Using framebuffer using OpenGL 3.2
GL debug messages:
Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fabric'
Universe: 400921fb54442d18
Type: Client (map_client.txt)
Graphics mode: fast
Render Distance: 8/8 chunks
Resource Packs: vanilla, fabric, custom-fog, disable_custom_worlds_advice, dynamic_fps, fabric-api, fabric-api-base, fabric-api-lookup-api-v1, fabric-biome-api-v1, fabric-block-api-v1, fabric-block-view-api-v2, fabric-blockrenderlayer-v1, fabric-client-tags-api-v1, fabric-command-api-v1, fabric-command-api-v2, fabric-commands-v0, fabric-containers-v0, fabric-content-registries-v0, fabric-convention-tags-v1, fabric-crash-report-info-v1, fabric-data-attachment-api-v1, fabric-data-generation-api-v1, fabric-dimensions-v1, fabric-entity-events-v1, fabric-events-interaction-v0, fabric-events-lifecycle-v0, fabric-game-rule-api-v1, fabric-item-api-v1, fabric-item-group-api-v1, fabric-key-binding-api-v1, fabric-keybindings-v0, fabric-lifecycle-events-v1, fabric-loot-api-v2, fabric-message-api-v1, fabric-mining-level-api-v1, fabric-model-loading-api-v1, fabric-models-v0, fabric-networking-api-v1, fabric-object-builder-api-v1, fabric-particles-v1, fabric-recipe-api-v1, fabric-registry-sync-v0, fabric-renderer-api-v1, fabric-renderer-indigo, fabric-renderer-registries-v1, fabric-rendering-data-attachment-v1, fabric-rendering-fluids-v1, fabric-rendering-v0, fabric-rendering-v1, fabric-resource-conditions-api-v1, fabric-resource-loader-v0, fabric-screen-api-v1, fabric-screen-handler-api-v1, fabric-sound-api-v1, fabric-transfer-api-v1, fabric-transitive-access-wideners-v1, fabricloader, immediatelyfast, infinite-music, keepthatmusic, krypton, lazydfu, legacy, lithium, minecart-turning, modmenu, taxfreelevels, walk-jog-run, yet_another_config_lib_v3, file/ClassicCraft (incompatible), legacy:legacy_waters_resourcepacks/legacy_waters
Current Language: en_us
Locale: en_US
CPU: 6x Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz

Fixed in version 1.4.4, thanks for reporting.