[PATCH] ACPI PCI Hotplug: add a BUG() where one should be

If there is a condition with the comment "should never happen" it is a good
place for a BUG() if it is ever reached.

drivers/pci/hotplug/acpiphp_glue.c

@@ -1180,7 +1180,8 @@ struct acpiphp_slot *get_slot_from_id(int id)
 	}
 
 	/* should never happen! */
-	err("%s: no object for id %d\n",__FUNCTION__, id);
+	err("%s: no object for id %d\n", __FUNCTION__, id);
+	WARN_ON(1);
 	return 0;
 }