Ignore basename failures

Commit 0210be22aebffc715103767922b431953f3693e1 introduced the
possibility of basename being called on an empty string.  Because
that can happen in normal operation (such as an x86_64 kernel,
in which case the PAE check will find nothing), don't allow the
basename error to kill the script.  Also ignore failures in the
second basename call so the proper error message is echoed.

Change-Id: I38a18af09ab24fda9c98cbf3ace8fd7acc6faef5
Merge "Ignore basename failures"