non-search tags: distribution not loading correctly

ProdClone build 99
Account Settings >> Non-Search Tags

When you add a distribution that already exists, instead of getting an error,
the dialog box goes blank and doesn't load.

Note: This happens on production, too.

Also, on client-pc, go to A Test Account B and try to add the
distribution "test". Because this distribution is not in the drop-down in the
Add Tag dialog, it should allow this distribution to be made. Not sure if
this happens in production. It did allow me to add the
distribution "tryagain", however.