Bettern handle NPE in RcsTestApp ChatActivity

1) In some cases, Exception#getMessage() can return null, which will
not work nicely with Log util. Instead use toString, which handles
the null condition better.

2) Fix NPE generation in RegistrationControllerImpl, since it looks
like some carriers do not populate service routes.

Test: manual
Change-Id: Ie2572d2858709e0f62c0d6059883fa1b694dee63
3 files changed