Fixed a bug where rbt land was unable to determine the approval state  of a review request.
Fixed a bug where rbt land was unable to determine the approval state  of a review request.

Fixed a bug where rbt land was unable to determine the approval state
of a review request.

This change introduces default values to `is_rr_approved` and
`approval_failure` before attempting to retrieve information from the
review request. In the event an exception is encountered, RBTools will
fail gracefully without disclosing a stack trace.

Testing Done:
Ran the land command multiple times, and observed its functionality
with and without ship-its. Noted that functionality is unaffected
for normal use cases.

Bugs closed: 4024

Reviewed at https://reviews.reviewboard.org/r/8401/

reviewboard/rbtools,reviewboard/rbtools,reviewboard/rbtools