I'm playing on 1.12.2 with Litemod and Forge.
I'm using malilib-1.12.2-0.9.0 and litematica-1.12.2-0.0.0-dev.20200615.020552
Whenever I try to play Minecraft with both mods in my folder, the game crashes. The game doesn't crash when either are by themselves.
To reproduce, put both mods in the mod folder and run the game.
Here's my crash log:

---- Minecraft Crash Report ----

WARNING: coremods are present:
Contact their authors BEFORE contacting forge

// Shall we play a game?

Time: 7/8/20 8:51 PM
Description: Unexpected error

java.lang.NoClassDefFoundError: fi/dy/masa/malilib/interfaces/IRangeChangeListener
at net.minecraft.client.Minecraft.handler$onRunTickStart$zhc000(Minecraft.java:5867)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1098)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: fi.dy.masa.malilib.interfaces.IRangeChangeListener
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 11 more
Caused by: java.lang.NullPointerException

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

-- System Details --
Details:
Minecraft Version: 1.12.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 328360888 bytes (313 MB) / 872415232 bytes (832 MB) up to 2147483648 bytes (2048 MB)
LiteLoader Brand: 1.12.2-SNAPSHOT-r4CC2BB0-b4-4
LiteLoader Mods: none
LaunchWrapper: 26 active transformer(s)
- Transformer: net.minecraftforge.fml.common.asm.transformers.PatchingTransformer
- Transformer: org.spongepowered.asm.mixin.transformer.Proxy
- Transformer: optifine.OptiFineClassTransformer
- Transformer: $wrapper.net.minecraftforge.fml.common.asm.transformers.SideTransformer
- Transformer: $wrapper.net.minecraftforge.fml.common.asm.transformers.EventSubscriptionTransformer
- Transformer: $wrapper.net.minecraftforge.fml.common.asm.transformers.EventSubscriberTransformer
- Transformer: $wrapper.net.minecraftforge.fml.common.asm.transformers.SoundEngineFixTransformer
- Transformer: com.mumfrey.liteloader.transformers.event.EventProxyTransformer
- Transformer: com.mumfrey.liteloader.launch.LiteLoaderTransformer
- Transformer: com.mumfrey.liteloader.client.transformers.CrashReportTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.DeobfuscationTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.AccessTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.ModAccessTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.ItemStackTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.ItemBlockTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.ItemBlockSpecialTransformer
- Transformer: net.minecraftforge.fml.common.asm.transformers.PotionEffectTransformer
- Transformer: org.spongepowered.asm.mixin.transformer.Proxy
- Transformer: org.spongepowered.asm.mixin.transformer.Proxy
- Transformer: net.minecraftforge.fml.common.asm.transformers.TerminalTransformer
- Transformer: org.spongepowered.asm.mixin.transformer.Proxy
- Transformer: com.mumfrey.liteloader.transformers.event.EventTransformer
- Transformer: com.mumfrey.liteloader.common.transformers.LiteLoaderPacketTransformer
- Transformer: com.mumfrey.liteloader.transformers.event.json.ModEventInjectionTransformer
- Transformer: org.spongepowered.asm.mixin.transformer.Proxy
- Transformer: net.minecraftforge.fml.common.asm.transformers.ModAPITransformer
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.42 Powered by Forge 14.23.5.2847 Optifine OptiFine_1.12.2_HD_U_F5 7 mods loaded, 7 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

| State  | ID            | Version      | Source                                      | Signature |
|:------ |:------------- |:------------ |:------------------------------------------- |:--------- |
| LCHIJA | minecraft     | 1.12.2       | minecraft.jar                               | None      |
| LCHIJA | mcp           | 9.42         | minecraft.jar                               | None      |
| LCHIJA | FML           | 8.0.99.99    | forge-1.12.2-14.23.5.2847.jar               | None      |
| LCHIJA | forge         | 14.23.5.2847 | forge-1.12.2-14.23.5.2847.jar               | None      |
| LCHIJA | lunatriuscore | 1.2.0.42     | LunatriusCore-1.12.2-1.2.0.42-universal.jar | None      |
| LCHIJA | schematica    | 1.8.0.169    | Schematica-1.12.2-1.8.0.169-universal.jar   | None      |
| LCHIJA | worldedit     | 6.1.10       | worldedit-forge-mc1.12.2-6.1.10-dist.jar    | None      |

Loaded coremods (and transformers): 
GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.6.0 NVIDIA 451.48' Renderer: 'GeForce GTX 1660 Ti/PCIe/SSE2'
Launched Version: 1.12.2-forge1.12.2-14.23.5.2847
LWJGL: 2.9.4
OpenGL: GeForce GTX 1660 Ti/PCIe/SSE2 GL version 4.6.0 NVIDIA 451.48, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.

Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fml,forge,LiteLoader'
Type: Client (map_client.txt)
Resource Packs: 
Current Language: English (US)
Profiler Position: N/A (disabled)
CPU: 8x Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
OptiFine Version: OptiFine_1.12.2_HD_U_F5
OptiFine Build: 20191204-141934
Render Distance Chunks: 24
Mipmaps: 4
Anisotropic Filtering: 1
Antialiasing: 0
Multitexture: false
Shaders: null
OpenGlVersion: 4.6.0 NVIDIA 451.48
OpenGlRenderer: GeForce GTX 1660 Ti/PCIe/SSE2
OpenGlVendor: NVIDIA Corporation
CpuCount: 8

Why did I not respond to this earlier? 🤔

Anyway, you are using a very old malilib version (0.9.0). You need the latest (currently 0.10.0-dev.29) version to use with the latest Litematica builds. https://masa.dy.fi/mcmods/client_mods/?mcver=1.12.2