Add

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

@@ -68,6 +68,10 @@ public class SWInventory implements Listener {
         callbacks.put(-1, inventoryClickEvent -> c.clicked(null));
     }
 
+    public void addCloseRunable(Runnable c) {
+        callbacks.put(-1, inventoryClickEvent -> c.run());
+    }
+
     public void setItem(int pos, ItemStack itemStack, InvCallback c) {
         inventory.setItem(pos, itemStack);
         callbacks.put(pos, inventoryClickEvent -> c.clicked(inventoryClickEvent.getClick()));