When I try to start up minecraft 1.8 this happens...

 

---- Minecraft Crash Report ----

WARNING: coremods are present:
  PlayerAPIPlugin (PlayerAPI-1.8-1.1.jar)
Contact their authors BEFORE contacting forge

// Everything's going to plan. No, really, that was supposed to happen.

Time: 11/15/18 6:21 PM
Description: Initializing game

java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    Config.getDefiningResourcePack(Lnet/minecraft/network/play/server/S19PacketEntityHeadLook;)Lnet/minecraft/client/gui/GuiScreenResourcePacks; @48: areturn
  Reason:
    Type 'net/minecraft/client/gui/inventory/GuiEditSign' (current frame, stack[0]) is not assignable to 'net/minecraft/client/gui/GuiScreenResourcePacks' (from method signature)
  Current Frame:
    bci: @48
    flags: { }
    locals: { 'net/minecraft/network/play/server/S19PacketEntityHeadLook', '[Lnet/minecraft/client/gui/GuiScreenResourcePacks;' }
    stack: { 'net/minecraft/client/gui/inventory/GuiEditSign' }
  Bytecode:
    0x0000000: b803 494c 2bbe 0464 3d1c 9b00 192b 1c32
    0x0000010: 4e2d 2ab9 0373 0200 9900 052d b084 02ff
    0x0000020: a7ff e9b8 034d 2ab6 0374 9900 07b8 034d
    0x0000030: b001 b0                                
  Stackmap Table:
    append_frame(@9,Object[#828],Integer)
    same_frame(@29)
    chop_frame(@35,1)
    same_frame(@49)

    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
    at java.lang.Class.getField0(Class.java:2975)
    at java.lang.Class.getField(Class.java:1701)
    at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:196)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:412)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:325)
    at net.minecraft.client.main.Main.main(SourceFile:120)
    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)

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

-- Head --
Stacktrace:
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
    at java.lang.Class.getField0(Class.java:2975)
    at java.lang.Class.getField(Class.java:1701)
    at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:196)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:412)

-- Initialization --
Details:
Stacktrace:
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:325)
    at net.minecraft.client.main.Main.main(SourceFile:120)
    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)

-- System Details --
Details:
    Minecraft Version: 1.8
    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: 611311880 bytes (582 MB) / 771751936 bytes (736 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: 
    Loaded coremods (and transformers): 
PlayerAPIPlugin (PlayerAPI-1.8-1.1.jar)
  api.player.forge.PlayerAPITransformer
    Launched Version: 1.8-Forge11.14.1.1334
    LWJGL: 2.9.1
    OpenGL: GeForce GT 705/PCIe/SSE2 GL version 4.6.0 NVIDIA 388.73, 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: No
    Is Modded: Definitely; Client brand changed to 'fml,forge'
    Type: Client (map_client.txt)
    Resource Packs: []
    Current Language: ~~ERROR~~ NullPointerException: null
    Profiler Position: N/A (disabled)

 

Any help would be much appreciated!

1 hour ago, TheHecticGamer said:

PlayerAPIPlugin (PlayerAPI-1.8-1.1.jar)

Try removing this (core)mod.

Also you should stop using 1.8 because we don't support anything below 1.8.9 on this forum anymore due to its age. We simply don't know how to help you anymore. You can go to the Minecraft Forum where I think that they still still support older versions, or update to a modern version of Minecraft (the latest version or the one before it) to receive support on this forum.