Prevent crashes when the used item cannot be found on the player

* re https://github.com/SleepyTrousers/EnderIO/issues/4218

src/main/java/biomesoplenty/common/util/entity/PlayerUtil.java

@@ -30,6 +30,6 @@ public class PlayerUtil
                 return hand;
         }
         
-        return null;
+        return EnumHand.MAIN_HAND;
     }
 }