[JTC] Sending an empty traj topic overrides the current action goal

[christophfroehlich]

Sending an empty trajectory message from the topic interface (not the action interface) will override the current action goal and not abort the action.

          I think it will be overridden, but it should not be. The explanation is correct, but I  don't think it is desirable.

Originally posted by @destogl in #566 (comment)

[github-actions]

This issue is being labeled as stale because it has been open 45 days with no activity. It will be automatically closed after another 45 days without follow-ups.