i2o_driver_register() initalizes event queue for driver only when
drv->event is set.  So similarly the event queue should be destroyed only
when drv->event is set in the error path.  Otherwise destroy_workqueue()
will called with NULL.
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
        }
 
        rc = driver_register(&drv->driver);
-       if (rc)
-               destroy_workqueue(drv->event_queue);
+       if (rc) {
+               if (drv->event) {
+                       destroy_workqueue(drv->event_queue);
+                       drv->event_queue = NULL;
+               }
+       }
 
        return rc;
 };