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.

Ran the land command multiple times, and observed its functionality 

with and without ship-its. Noted that functionality is unaffected 

for normal use cases.