wifi: ieee80211: check for NULL in ieee80211_mle_size_ok()

For simplicity, we may want to pass a NULL element, and
while we should then pass also a zero length, just be a
bit more careful here.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240318184907.4d983653cb8d.Ic3ea99b60c61ac2f7d38cb9fd202a03c97a05601@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/linux/ieee80211.h

@@ -5166,7 +5166,7 @@ static inline bool ieee80211_mle_size_ok(const u8 *data, size_t len)
 	bool check_common_len = false;
 	u16 control;
 
-	if (len < fixed)
+	if (!data || len < fixed)
 		return false;
 
 	control = le16_to_cpu(mle->control);