Allow 0 and otherwise empty forwards to filter out and pass validation

[huumn]

Someone dm'd sn's X account that they were stuck at this screen. They thought 0 was equivalent to blank so perhaps it should be.

The solution is to allow these to pass - but ONLY on clientside validation (server side uses the same validation so we don't want to allow the client to pass '0' forwards to us) - then filter these out before calling the mutuation. validation ideally.