Fix hostapd PMKSA_ADD with Authenticator disabled

This function can get called with hapd->wpa_auth == NULL from the
control interface handler, so explicitly check for that.

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

src/ap/wpa_auth.c

@@ -4831,7 +4831,7 @@ int wpa_auth_pmksa_add2(struct wpa_authenticator *wpa_auth, const u8 *addr,
 			const u8 *pmk, size_t pmk_len, const u8 *pmkid,
 			int session_timeout, int akmp)
 {
-	if (wpa_auth->conf.disable_pmksa_caching)
+	if (!wpa_auth || wpa_auth->conf.disable_pmksa_caching)
 		return -1;
 
 	wpa_hexdump_key(MSG_DEBUG, "RSN: Cache PMK (2)", pmk, PMK_LEN);