Solved a bug with a blocked mutex when waiting a replay from the GPS.

src/asterx1_gps.cpp

@@ -1216,7 +1216,9 @@ void CasteRx1::send_command(const std::string &cmd)
   try{
     this->gps_access.enter();
     this->serial_port->write((unsigned char *)cmd.c_str(),cmd.size());
+    this->gps_access.exit();
     this->event_server->wait_all(events,500);
+    this->gps_access.enter();
     // compare the answer with the command
     reply=this->reply_queue.front();// get the reply
     this->reply_queue.pop();// remove it from the queue