Fix NPE

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

@@ -153,7 +153,7 @@ public class SWInventory implements Listener {
 
         if (callbacks.containsKey(e.getRawSlot()) && callbacks.get(e.getRawSlot()) != null) {
             e.setCancelled(true);
-            Core.getInstance().getLogger().info("[SWINV] " + e.getWhoClicked().getName() + " " + e.getClick().name() + " clicked " + e.getRawSlot() + " on " + e.getCurrentItem().getItemMeta().getDisplayName() + " in " + e.getView().getTitle());
+            Core.getInstance().getLogger().info("[SWINV] " + e.getWhoClicked().getName() + " " + e.getClick().name() + " clicked " + e.getRawSlot() + " on " + (e.getCurrentItem() != null ? e.getCurrentItem().getItemMeta().getDisplayName() : "[EMPTY]") + " in " + e.getView().getTitle());
             callbacks.get(e.getRawSlot()).accept(e);
         }
     }