Kick for invalid carried item.

src/main/java/net/minecraft/server/NetServerHandler.java

@@ -830,6 +830,7 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
             this.player.inventory.itemInHandIndex = packet16blockitemswitch.itemInHandIndex;
         } else {
             logger.warning(this.player.name + " tried to set an invalid carried item");
+            this.disconnect("Nope!"); // CraftBukkit
         }
     }