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

@@ -68,13 +68,17 @@ public class SWInventory implements Listener {
         callbacks.put(-1, inventoryClickEvent -> c.clicked(null));
     }
 
-    public void addCloseRunable(Runnable c) {
+    public void addCloseRunnable(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()));
+        if(c != null) {
+            callbacks.put(pos, inventoryClickEvent -> c.clicked(inventoryClickEvent.getClick()));
+        } else {
+            callbacks.remove(pos);
+        }
     }
 
     public void setItem(int pos, SWItem item) {