[Autoroller] Skip revision if no builds yet
[Autoroller] Skip revision if no builds yet

Bug: skia:10010
Change-Id: I913b5960e2d2f397fa38e206b704b85ab6e62a62
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/276213
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot