Prevent fatal errors in urlgenerator

Reviewed the UrlGenerator for oportunites to generate fatal
errors.  UrlGenerator should now always output catchable errors
of one sort or another and not fatal.

Bug: 60906
Change-Id: Ied0563ccd5e06d6c189c919a0e6c1d9c62faf63c
(cherry picked from commit 68594255e5f028ed7ae63aead13f1721815a2b3f)