libertas: fix potential NULL-pointer dereference

The code wants to check if there's a channel and it is not disabled,
but it used to check if channel is not NULL and accessed the channel
struct if this check failed.
Signed-off-by: Sven Neumann <s.neumann@raumfeld.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/cfg.c

@@ -619,7 +619,7 @@ static int lbs_ret_scan(struct lbs_private *priv, unsigned long dummy,
 				     print_ssid(ssid_buf, ssid, ssid_len),
 				     LBS_SCAN_RSSI_TO_MBM(rssi)/100);
 
-			if (channel ||
+			if (channel &&
 			    !(channel->flags & IEEE80211_CHAN_DISABLED))
 				cfg80211_inform_bss(wiphy, channel,
 					bssid, le64_to_cpu(*(__le64 *)tsfdesc),