amend: Don't attempt to lookup topics if no github remote

[jerry-skydio]

If we're in a repo with no remote, or no github remote, don't
attempt the topics lookup at all as we assume the user isn't
using "revup upload" in this repo.

This slightly speeds up and avoids some errors.

Topic: amend_lookup
Reviewers: brian-k

[jerry-skydio]

Reviews in this chain:
└#80 amend: Don't attempt to lookup topics if no github remote

[jerry-skydio]

#	head	base	diff	date	summary
0	5a5366d6	311ff10d	diff	Oct 24 17:41 PM	3 files changed, 51 insertions(+), 40 deletions(-)