WNM: Fix Sleep Mode AP processing in open network

The previous version could end up calling WPA authenticator routines
even though the authenticator had not been initialized and this could
result in NULL pointer dereference.

Signed-hostap: Jouni Malinen <j@w1.fi>

src/ap/wpa_auth.c

@@ -2457,7 +2457,7 @@ static int wpa_group_update_sta(struct wpa_state_machine *sm, void *ctx)
 /* update GTK when exiting WNM-Sleep Mode */
 void wpa_wnmsleep_rekey_gtk(struct wpa_state_machine *sm)
 {
-	if (sm->is_wnmsleep)
+	if (sm == NULL || sm->is_wnmsleep)
 		return;
 
 	wpa_group_update_sta(sm, NULL);
@@ -2466,7 +2466,8 @@ void wpa_wnmsleep_rekey_gtk(struct wpa_state_machine *sm)
 
 void wpa_set_wnmsleep(struct wpa_state_machine *sm, int flag)
 {
-	sm->is_wnmsleep = !!flag;
+	if (sm)
+		sm->is_wnmsleep = !!flag;
 }