I have installed the forge and the other mod this is the crash report:

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 3/27/21 4:01 PM
Description: Ticking entity

java.lang.NullPointerException: Ticking entity
at melonslise.lambda.common.entity.alien.EntityHeadcrab.func_70074_a(EntityHeadcrab.java:97)
at net.minecraft.entity.EntityLivingBase.func_70645_a(EntityLivingBase.java:1181)
at net.minecraft.entity.passive.EntityVillager.func_70645_a(EntityVillager.java:536)
at net.minecraft.entity.EntityLivingBase.func_70097_a(EntityLivingBase.java:1023)
at net.minecraft.entity.monster.EntityMob.func_70652_k(EntityMob.java:99)
at melonslise.lambda.common.entity.alien.EntityHeadcrab.bite(EntityHeadcrab.java:86)
at melonslise.lambda.common.entity.alien.EntityHeadcrab$AILatch.func_75246_d(EntityHeadcrab.java:269)
at net.minecraft.entity.ai.EntityAITasks.func_75774_a(SourceFile:129)
at net.minecraft.entity.EntityLiving.func_70626_be(EntityLiving.java:763)
at net.minecraft.entity.EntityLivingBase.func_70636_d(EntityLivingBase.java:2359)
at net.minecraft.entity.EntityLiving.func_70636_d(EntityLiving.java:577)
at net.minecraft.entity.monster.EntityMob.func_70636_d(EntityMob.java:45)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:2179)
at net.minecraft.entity.EntityLiving.func_70071_h_(EntityLiving.java:295)
at net.minecraft.entity.monster.EntityMob.func_70071_h_(EntityMob.java:50)
at net.minecraft.world.World.func_72866_a(World.java:1996)
at net.minecraft.world.WorldServer.func_72866_a(WorldServer.java:832)
at net.minecraft.world.World.func_72870_g(World.java:1958)
at net.minecraft.world.World.func_72939_s(World.java:1762)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:613)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:767)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
at java.lang.Thread.run(Thread.java:745)

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

-- Head --
Thread: Server thread
Stacktrace:
at melonslise.lambda.common.entity.alien.EntityHeadcrab.func_70074_a(EntityHeadcrab.java:97)
at net.minecraft.entity.EntityLivingBase.func_70645_a(EntityLivingBase.java:1181)
at net.minecraft.entity.passive.EntityVillager.func_70645_a(EntityVillager.java:536)
at net.minecraft.entity.EntityLivingBase.func_70097_a(EntityLivingBase.java:1023)
at net.minecraft.entity.monster.EntityMob.func_70652_k(EntityMob.java:99)
at melonslise.lambda.common.entity.alien.EntityHeadcrab.bite(EntityHeadcrab.java:86)
at melonslise.lambda.common.entity.alien.EntityHeadcrab$AILatch.func_75246_d(EntityHeadcrab.java:269)
at net.minecraft.entity.ai.EntityAITasks.func_75774_a(SourceFile:129)
at net.minecraft.entity.EntityLiving.func_70626_be(EntityLiving.java:763)
at net.minecraft.entity.EntityLivingBase.func_70636_d(EntityLivingBase.java:2359)
at net.minecraft.entity.EntityLiving.func_70636_d(EntityLiving.java:577)
at net.minecraft.entity.monster.EntityMob.func_70636_d(EntityMob.java:45)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:2179)
at net.minecraft.entity.EntityLiving.func_70071_h_(EntityLiving.java:295)
at net.minecraft.entity.monster.EntityMob.func_70071_h_(EntityMob.java:50)
at net.minecraft.world.World.func_72866_a(World.java:1996)
at net.minecraft.world.WorldServer.func_72866_a(WorldServer.java:832)
at net.minecraft.world.World.func_72870_g(World.java:1958)

-- Entity being ticked --
Details:
Entity Type: lambda:headcrab (melonslise.lambda.common.entity.alien.EntityHeadcrab)
Entity ID: 14687
Entity Name: Headcrab
Entity's Exact location: 35.99, 69.18, 125.91
Entity's Block location: World: (35,69,125), Chunk: (at 3,4,13 in 2,7; contains blocks 32,0,112 to 47,255,127), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0.00, -0.16, 0.00
Entity's Passengers: []
Entity's Vehicle: ERROR NullPointerException: null
Stacktrace:
at net.minecraft.world.World.func_72939_s(World.java:1762)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:613)

-- Affected level --
Details:
Level name: Half-Life Mod
All players: 1 total; [EntityPlayerMP['93719'/915, l='Half-Life Mod', x=23.35, y=72.98, z=99.37]]
Chunk stats: ServerChunkCache: 689 Drop: 0
Level seed: 1000648212953417311
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (0,64,-39), Chunk: (at 0,4,9 in 0,-3; contains blocks 0,0,-48 to 15,255,-33), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
Level time: 6025 game time, 6025 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 103713 (now: false), thunder time: 139970 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:767)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
at java.lang.Thread.run(Thread.java:745)

-- 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: 514486304 bytes (490 MB) / 1174405120 bytes (1120 MB) up to 2147483648 bytes (2048 MB)
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: 12, tallocated: 94
FML: MCP 9.42 Powered by Forge 14.23.5.2854 5 mods loaded, 5 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-1.12.2-14.23.5.2854.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| LCHIJA | forge     | 14.23.5.2854 | forge-1.12.2-14.23.5.2854.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| LCHIJA | lambda    | 0.0.2        | ProjectLambda-0.0.2.jar       | None                                     |

Loaded coremods (and transformers): 
GL info: ~~ERROR~~ RuntimeException: No OpenGL context found in the current thread.
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [EntityPlayerMP['93719'/915, l='Half-Life Mod', x=23.35, y=72.98, z=99.37]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'