pull_number undefined when action is running on push to master branch

[ppalucha]

Hi, we have action running fine on PRs, but when merging PR to master, the action fails with message:

Error: Action failed with error: Empty value for parameter 'pull_number': undefined

The workflow we use is just simple:

jobs:
  check-commit:
    runs-on: self-hosted-fleet
    steps:
      - name: Check commit message
        uses: ad1992/clean-commit-action@v0.2.0
        with:
          repo-token: ${{ secrets.GITHUB_TOKEN }}

[ad1992]

This action should only run on PR's. So you will need to mention that in the action as shown in example