Whenever I launch my pixelmon game, it will always crash. Describing this error message to me : 

 

 

 

Caused by: java.lang.ClassNotFoundException: net.minecraftforge.event.world.BlockEvent$EntityPlaceEvent
    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)
    ... 51 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: 375821512 bytes (358 MB) / 1073741824 bytes (1024 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: 0, tallocated: 0
    FML: MCP 9.42 Powered by Forge 14.23.5.2768 6 mods loaded, 6 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                                |
    |:----- |:------------- |:------------ |:----------------------------------- |:---------------------------------------- |
    | UCHI  | minecraft     | 1.12.2       | minecraft.jar                       | None                                     |
    | UCHI  | mcp           | 9.42         | minecraft.jar                       | None                                     |
    | UCHI  | FML           | 8.0.99.99    | forge-1.12.2-14.23.5.2768.jar       | e3c3d50c7c986df74c645c0ac54639741c90a557 |
    | UCHI  | forge         | 14.23.5.2768 | forge-1.12.2-14.23.5.2768.jar       | e3c3d50c7c986df74c645c0ac54639741c90a557 |
    | UCHI  | oreexcavation | 1.4.137      | OreExcavation-1.4.137.jar           | None                                     |
    | UCHEE | pixelmon      | 8.0.2        | Pixelmon-1.12.2-8.0.2-universal.jar | None                                     |

    Loaded coremods (and transformers): 
    GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.6.0 NVIDIA 445.87' Renderer: 'GeForce GTX 1660 Ti/PCIe/SSE2'

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Please update to a modern version of Minecraft to receive support.