Crash

[Client thread/ERROR] [FML]: Exception caught during firing event net.minecraftforge.fml.common.gameevent.TickEvent$ClientTickEvent@180e1754:
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_45]
at java.util.ArrayList$Itr.next(ArrayList.java:851) ~[?:1.8.0_45]
at com.DavidM1A2.common.MCACommonLibrary.animation.AnimTickHandler.onClientTick(AnimTickHandler.java:36) ~[AnimTickHandler.class:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_19_AnimTickHandler_onClientTick_ClientTickEvent.invoke(.dynamic) ~[?:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:55) ~[ASMEventHandler.class:?]
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:138) [EventBus.class:?]
at net.minecraftforge.fml.common.FMLCommonHandler.onPreClientTick(FMLCommonHandler.java:366) [FMLCommonHandler.class:?]
at net.minecraft.client.Minecraft.runTick(Minecraft.java:1706) [Minecraft.class:?]
at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1086) [Minecraft.class:?]
at net.minecraft.client.Minecraft.run(Minecraft.java:375) [Minecraft.class:?]
at net.minecraft.client.main.Main.main(Main.java:117) [Main.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_45]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_45]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_45]
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_45]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.11.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.11.jar:?]
at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source) [start/:?]
at GradleStart.main(Unknown Source) [start/:?]