Action fails on push event for first push on new branch

[sguha00]

Description of the bug

Action fails on push event for first push on new branch

To Reproduce

1. Enable this action on a push event
2. Create a new branch and make a commit
3. Actions fails with

  Base commit: 0000000000000000000000000000000000000000
  Head commit: 843b31e8dd125aafb7d43fd5d1f3d021a43b32fd
Error: HttpError: Not Found```

#### Expected behavior

Preview should success

#### Actual behavior

When checking if a new version of the dev client should be build, the base commit is invalid so the `compareCommits` call fails

### Additional context

The first `push` event on a new branch has a `before` of all 0's. Instead `base_ref` should be used