cfg80211: "fix" 11d oops

This "fixes" the 11d oops I was seeing. This needs some more work but I
cannot work on it now.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/reg.c

@@ -989,6 +989,9 @@ void regulatory_hint_11d(struct wiphy *wiphy,
 	u32 checksum = 0;
 	enum environment_cap env = ENVIRON_ANY;
 
+	if (!last_request)
+		return;
+
 	mutex_lock(&cfg80211_drv_mutex);
 
 	/* IE len must be evenly divisible by 2 */