Can someone help me with this? I installed mgnesium mod and made change in toml file from 1.18 to 1.18.1 and now autoreglib is not loading. Kindly help me fix this.
A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Render thread
Stacktrace:
at java.util.Objects.requireNonNull(Objects.java:208) ~[?:?] {re:mixin}
-- MOD autoreglib --
Details:
Mod File: AutoRegLib-1.7-52.jar
Failure message: AutoRegLib (autoreglib) encountered an error during the complete event phase
java.lang.NullPointerException: null
Mod Version: 1.7-52
Mod Issue URL: https://github.com/Vazkii/AutoRegLib
Exception message: java.lang.NullPointerException
Stacktrace:
at java.util.Objects.requireNonNull(Objects.java:208) ~[?:?] {re:mixin}
at net.minecraft.client.color.block.BlockColors.handler$zbd000$preRegisterColor(BlockColors.java:532) ~[client-1.18.1-20211210.034407-srg.jar%2367!/:?] {re:mixin,pl:runtimedistcleaner:A,re:classloading,pl:mixin:A,pl:runtimedistcleaner:A}
at net.minecraft.client.color.block.BlockColors.m_92589_(BlockColors.java) ~[client-1.18.1-20211210.034407-srg.jar%2367!/:?] {re:mixin,pl:runtimedistcleaner:A,re:classloading,pl:mixin:A,pl:runtimedistcleaner:A}
at vazkii.arl.util.RegistryHelper.loadCompleteClient(RegistryHelper.java:134) ~[AutoRegLib-1.7-52.jar%2352!/:1.7-52] {re:classloading}
at vazkii.arl.util.RegistryHelper.lambda$loadComplete$3(RegistryHelper.java:118) ~[AutoRegLib-1.7-52.jar%2352!/:1.7-52] {re:classloading}
at net.minecraftforge.fml.DistExecutor.unsafeRunWhenOn(DistExecutor.java:125) ~[fmlcore-1.18.1-39.0.79.jar%2368!/:?] {}
at net.minecraftforge.fml.DistExecutor.runWhenOn(DistExecutor.java:109) ~[fmlcore-1.18.1-39.0.79.jar%2368!/:?] {}
at vazkii.arl.util.RegistryHelper.loadComplete(RegistryHelper.java:118) ~[AutoRegLib-1.7-52.jar%2352!/:1.7-52] {re:classloading}
at vazkii.arl.AutoRegLib.loadComplete(AutoRegLib.java:29) ~[AutoRegLib-1.7-52.jar%2352!/:1.7-52] {re:classloading}
at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:247) ~[eventbus-5.0.3.jar%232!/:?] {}
at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:239) ~[eventbus-5.0.3.jar%232!/:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-5.0.3.jar%232!/:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-5.0.3.jar%232!/:?] {}
at net.minecraftforge.fml.javafmlmod.FMLModContainer.acceptEvent(FMLModContainer.java:120) ~[javafmllanguage-1.18.1-39.0.79.jar%2369!/:?] {}
at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:121) ~[fmlcore-1.18.1-39.0.79.jar%2368!/:?] {}
at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) ~[?:?] {}
at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) ~[?:?] {}
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {}
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {}
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {}

-- System Details --
Details:
Minecraft Version: 1.18.1
Minecraft Version ID: 1.18.1
Operating System: Windows 10 (amd64) version 10.0
Java Version: 17.0.1, Microsoft
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Microsoft
Memory: 7442292288 bytes (7097 MiB) / 8355053568 bytes (7968 MiB) up to 23622320128 bytes (22528 MiB)
CPUs: 16
Processor Vendor: AuthenticAMD
Processor Name: AMD Ryzen 7 2700 Eight-Core Processor
Identifier: AuthenticAMD Family 23 Model 8 Stepping 2
Microarchitecture: Zen+
Frequency (GHz): 3.20
Number of physical packages: 1
Number of physical CPUs: 8
Number of logical CPUs: 16
Graphics card #0 name: NVIDIA GeForce GTX 1650
Graphics card #0 vendor: NVIDIA (0x10de)
Graphics card #0 VRAM (MB): 4095.00
Graphics card #0 deviceId: 0x1f82
Graphics card #0 versionInfo: DriverVersion=30.0.15.1109
Memory slot #0 capacity (MB): 16384.00
Memory slot #0 clockSpeed (GHz): 2.67
Memory slot #0 type: DDR4
Memory slot #1 capacity (MB): 16384.00
Memory slot #1 clockSpeed (GHz): 2.67
Memory slot #1 type: DDR4
Virtual memory max (MB): 38095.01
Virtual memory used (MB): 16487.03
Swap memory total (MB): 5376.00
Swap memory used (MB): 18.95
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx22G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
ModLauncher: 9.1.0+9.1.0+main.6690ee51
ModLauncher launch target: forgeclient
ModLauncher naming: srg
ModLauncher services:
mixin PLUGINSERVICE
eventbus PLUGINSERVICE
object_holder_definalize PLUGINSERVICE
runtime_enum_extender PLUGINSERVICE
capability_token_subclass PLUGINSERVICE
accesstransformer PLUGINSERVICE
runtimedistcleaner PLUGINSERVICE
mixin TRANSFORMATIONSERVICE
fml TRANSFORMATIONSERVICE
FML Language Providers:
[email protected]
javafml@null
Mod List:
client-1.18.1-20211210.034407-srg.jar |Minecraft |minecraft |1.18.1 |DONE |Manifest: a1:d4:5e:04:4f:d3:d6:e0:7b:37:97:cf:77:b0:de:ad:4a:47:ce:8c:96:49:5f:0a:cf:8c:ae:b2:6d:4b:8a:3f
clienttweaks-forge-1.18-7.0.0.jar |Client Tweaks |clienttweaks |7.0.0 |DONE |Manifest: NOSIGNATURE
morevillagers-FORGE-1.18.1-3.1.1.jar |More Villagers |morevillagers |3.1.1 |DONE |Manifest: NOSIGNATURE
MouseTweaks-forge-mc1.18-2.21.jar |Mouse Tweaks |mousetweaks |2.21 |DONE |Manifest: NOSIGNATURE
forgeautofish-4.0.0-1.18.x.jar |AutoFish for Forge |forgeautofish |4.0.0 |DONE |Manifest: NOSIGNATURE
magnesium-0.4.0-alpha6.jar |Magnesium |magnesium |0.4.0-alpha5 |DONE |Manifest: NOSIGNATURE
balm-2.4.1+0.jar |Balm |balm |2.4.1+0 |DONE |Manifest: NOSIGNATURE
jei-1.18.1-9.2.1.69.jar |Just Enough Items |jei |9.2.1.69 |DONE |Manifest: NOSIGNATURE
cloth-config-6.1.50-forge.jar |Cloth Config v4 API |cloth_config |6.1.50 |DONE |Manifest: NOSIGNATURE
forge-1.18.1-39.0.79-universal.jar |Forge |forge |39.0.79 |DONE |Manifest: 84:ce:76:e8:45:35:e4:0e:63:86:df:47:59:80:0f:67:6c:c1:5f:6e:5f:4d:b3:54:47:1a:9f:7f:ed:5e:f2:90
flywheel-forge-1.18-0.6.0.jar |Flywheel |flywheel |1.18-0.6.0 |DONE |Manifest: NOSIGNATURE
FastLeafDecay-27.2.jar |FastLeafDecay |fastleafdecay |27.2 |DONE |Manifest: NOSIGNATURE
CosmeticArmorReworked-1.18.1-v1a.jar |CosmeticArmorReworked |cosmeticarmorreworked |1.18.1-v1a |DONE |Manifest: 5e:ed:25:99:e4:44:14:c0:dd:89:c1:a9:4c:10:b5:0d:e4:b1:52:50:45:82:13:d8:d0:32:89:67:56:57:01:53
create-mc1.18.1_v0.4d.jar |Create |create |0.4d |DONE |Manifest: NOSIGNATURE
comforts-forge-1.18-5.0.0.1.jar |Comforts |comforts |1.18-5.0.0.1 |DONE |Manifest: NOSIGNATURE
AutoRegLib-1.7-52.jar |AutoRegLib |autoreglib |1.7-52 |ERROR |Manifest: NOSIGNATURE
Quark-3.0-334.jar |Quark |quark |3.0-334 |DONE |Manifest: NOSIGNATURE
Flywheel Backend: GL33 Instanced Arrays
Crash Report UUID: 8e82f5af-db30-4be5-966e-24026070e6b0
FML: 39.0
Forge: net.minecraftforge:39.0.79

crash-2022-02-23_21.07.13-fml.txt

I had the exact same problem, turns out I was using an outdated version of autoreglib, same as you, switching to the new version seems to have fixed it.