Add this qualifier

src/main/java/appeng/tile/inventory/AppEngInternalInventory.java

@@ -317,7 +317,7 @@ public class AppEngInternalInventory implements IInventory, Iterable<ItemStack>
 	{
 		for( int x = 0; x < this.size; x++ )
 		{
-			setInventorySlotContents( x,null );
+			this.setInventorySlotContents( x,null );
 		}
 	}
 }