Make sure `offset` is an integer
Summary:
Older git versions allowed the `--skip` to get empty string as value and interpreted that to an int.
We were sending `null` in some places where we wanted a `0`, so it all worked out.
Since https://git.kernel.org/pub/scm/git/git.git/commit/revision.c?id=71a1e94821666909b7b2bd62a36244c601f8430e git fails when provided empty string for an integer.
See Q124 and T15783.
Test Plan: Have recent git version (that fails with `--skip ''`, navigate to `/diffusion/1/history/master/`) - see history.
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: aklapper, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D25575