Allow empty commits to avoid errors when testing existing refs

Author: lbianchi-lbl

.github/workflows/test-self.yml

@@ -60,7 +60,7 @@ jobs:
           git config --global push.autoSetupRemote true
           git add .github/workflows/*.yml
           git status -vv
-          git commit -m "Test $WORKFLOW_SHORT_LINK" -m "Test $WORKFLOW_FULL_LINK"
+          git commit --allow-empty -m "Test $WORKFLOW_SHORT_LINK" -m "Test $WORKFLOW_FULL_LINK"
           git push -f
           echo "CALLER_SHA=$(git log -n 1 --format='%H')" >> $GITHUB_ENV
       - name: Show link to access caller workflow runs