fixed gets_shirt to do the correct thing both precon and at the con

This was a workaround I added awhile back with a note about needing to fix it later.  It's now later :)

Basically, the motivation here is that before the event, we want people to be marked as getting a shirt if they've signed up for enough hours.  But during the event, we only want them to be marked as getting a shirt if they've WORKED enough hours.