ART: Fast-fail empty other handlers in fault handling

Don't try to set up the nested handler environment if there are
no other handlers installed.

Stop-gap for the current setup without other handlers. There are
a myriad more issues before we can safely re-enable other handlers.

Bug: 28245957
Change-Id: I526aef82aa1ca2b6c4b1959858fe76231bc067d9
1 file changed