ci: handle cases when there's nothing to commit

.github/workflows/update-badge.yml

@@ -31,6 +31,6 @@ jobs:
         run: |
           git config user.email 'actions@github.com'
           git config user.name 'github-actions'
-          git add README.md
-          git commit -m 'update badges'
-          git push origin HEAD:${{ github.ref }}
+          if git commit -am 'update badges'; then
+            git push origin HEAD:${{ github.ref }}
+          fi