Build failed in base branch exist, but no PR with that branch is open

[StefMa]

Right now the code checks only if there is an PR open. If so, it will omit creating a PR. Otherwise it will try to push the branch and create the PR. However, if you close the PR but don't delete the branch (reason: you don't want to update to the latest gradle release. Therefore I close the PR, but keep the branch available. This is also how dependabot works), the build fails with "failed to push some refs to..."