Hotfix SWInventory

SpigotCore_Main/src/de/steamwar/inventory/SWInventory.java

@@ -162,5 +162,6 @@ public class SWInventory implements Listener {
         InventoryCloseEvent.getHandlerList().unregister(this);
         if(callbacks.containsKey(-1))
             callbacks.get(-1).accept(null);
+        open = false;
     }
 }