ci: skip adding PR labels if there are none to add (#25475)

.github/workflows/label-pr.yml

@@ -71,9 +71,11 @@ jobs:
             }
 
             // Add selected labels
+            if (labelsToAdd.length > 0) {
               github.rest.issues.addLabels({
                 issue_number: pullRequest.number,
                 owner: context.repo.owner,
                 repo: context.repo.repo,
                 labels: labelsToAdd
               })
+            }