fix: Error on publish message creation was ignored.

In the case of make_publish failure the client would just continue and
the error was ignored and not propagated to caller.

mqtt_client.c

@@ -1976,6 +1976,9 @@ static inline int mqtt_client_enqueue_publish(esp_mqtt_client_handle_t client, c
         int len, int qos, int retain, bool store)
 {
     int pending_msg_id = make_publish(client, topic, data, len, qos, retain);
+    if (pending_msg_id < 0) {
+        return -1;
+    }
     /* We have to set as pending all the qos>0 messages */
     //TODO: client->mqtt_state.outbound_message = publish_msg;
     if (qos > 0 || store) {