fixed concurrent exception thrown when removing animations from being ticked

src/main/java/noppes/npcs/controllers/data/AnimationData.java

@@ -167,8 +167,10 @@ public class AnimationData implements IAnimationData {
         }
 
         if (CustomNpcs.proxy.hasClient() && newAnim != null) {
-            CommonProxy.clientPlayingAnimations.remove(this.animation);
-            CommonProxy.clientPlayingAnimations.add(newAnim);
+            synchronized (CommonProxy.clientPlayingAnimations) {
+                CommonProxy.clientPlayingAnimations.remove(this.animation);
+                CommonProxy.clientPlayingAnimations.add(newAnim);
+            }
         }
         this.animation = newAnim;