wifi: do no crash when getting BSSID fails

https://bodhi.fedoraproject.org/updates/NetworkManager-1.0.6-7.fc23#comment-342089

(cherry picked from commit e9bc18d2a7)

src/devices/wifi/nm-device-wifi.c

@@ -1649,7 +1649,11 @@ try_fill_ssid_for_hidden_ap (NMAccessPoint *ap)
 	g_return_if_fail (nm_ap_get_ssid (ap) == NULL);
 
 	bssid = nm_ap_get_address (ap);
-	g_assert (bssid);
+	if (!bssid) {
+		nm_log_dbg (LOGD_WIFI, "failed to get BSSID for hidden AP %s",
+		            str_if_set (nm_ap_get_supplicant_path (ap), "(none)"));
+		return;
+	}
 
 	/* Look for this AP's BSSID in the seen-bssids list of a connection,
 	 * and if a match is found, copy over the SSID */