Don't Merge Pull Requests

[Kurt-von-Laven]

If this action is run on a pull_request event, it merges the pull request to the specified branch even if it has no commits to push. Not sure what the right way to handle that scenario is, but at least it shouldn't push if it hasn't made any commits. It's not advisable to run this action on pull_request, but it can be a difficult mistake to undo once it has happened. One way of checking whether there is anything to push would be to compare the project version before and after running cz bump. Another would be to use git diff --quiet <current_branch> origin/<current_branch>.