there's no direct way to stop an Action once it has started, one way I think to workaround the limitation is to maybe unload the action? not tested, just an idea, it may not work, try it and let us know.
Another idea, create a blank document, so your action attempts to continue running on it and it will fail, no big deal, it depends on what kind of error it gives you,
It would be desired for it to be possible to play actions which play a menu-item script which load and unload, or play, other actions. However due to another thread somewhere in the past on here, some one did say that this tangled way of playing the various items causes a crash. I need to test this out sometime!
too bad there is no real solution... In the case at hand, clearing the selection inside the script will cause the action to run into an error