Bug 760791 (tiltopen): Protect against null inputs
Bug 760791 (tiltopen): Protect against null inputs

This is the minimum part of the fix for this bug. A similar bug affects
other types, and there are tests to check, both of which are part of
Bug 706793 (nodenull)

mozilla/gcli,joewalker/gcli,mozilla/gcli,joewalker/gcli,mozilla/gcli