cfg80211: check wdev->netdev in connection work

If a P2P-Device is present and another virtual interface triggers
the connection work, the system crash because it tries to check
if the P2P-Device's netdev (which doesn't exist) is up. Skip any
wdevs that have no netdev to fix this.

Cc: stable@vger.kernel.org
Reported-by: YanBo <dreamfly281@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/sme.c

@@ -231,6 +231,9 @@ void cfg80211_conn_work(struct work_struct *work)
 	mutex_lock(&rdev->sched_scan_mtx);
 
 	list_for_each_entry(wdev, &rdev->wdev_list, list) {
+		if (!wdev->netdev)
+			continue;
+
 		wdev_lock(wdev);
 		if (!netif_running(wdev->netdev)) {
 			wdev_unlock(wdev);