Return nil for missing wiki page versions
Summary
This currently causes a NoMethodError
when passing a version which
does not exist, resulting in a Gitlab::Git::CommandError
/ HTTP 503
error on the GitLab side.
Background
This fixes the 503 error described in gitlab#206930 (closed). The other 500 error mentioned there needs to be fixed on the Rails side I think (it happens during the GRPC params validation).
Edited by GitLab Release Tools Bot