Fixed buffer overflow with auth key

src/comm/MAVLinkProtocol.cc

@@ -539,8 +539,8 @@ void MAVLinkProtocol::sendHeartbeat()
     {
         mavlink_message_t msg;
         mavlink_auth_key_t auth;
-        if (m_authKey.length() != MAVLINK_MSG_AUTH_KEY_FIELD_KEY_LEN) m_authKey.resize(MAVLINK_MSG_AUTH_KEY_FIELD_KEY_LEN);
-        strcpy(auth.key, m_authKey.toStdString().c_str());
+        memset(auth, 0, sizeof(auth));
+        memcpy(auth.key, m_authKey.toStdString().c_str(), qMin(m_authKey.length(), MAVLINK_MSG_AUTH_KEY_FIELD_KEY_LEN));
         mavlink_msg_auth_key_encode(getSystemId(), getComponentId(), &msg, &auth);
         sendMessage(msg);
     }