Delete Labels & IssueLabels on Repo Delete too (#15039) (#15051)

* Doctor: find IssueLabels without existing label

* Repo Delete: delete labels & issue_labels too

models/repo.go

@@ -1729,6 +1729,10 @@ func DeleteRepository(doer *User, uid, repoID int64) error {
 		return fmt.Errorf("deleteBeans: %v", err)
 	}
 
+	if err := deleteLabelsByRepoID(sess, repoID); err != nil {
+		return err
+	}
+
 	// Delete Issues and related objects
 	var attachmentPaths []string
 	if attachmentPaths, err = deleteIssuesByRepoID(sess, repoID); err != nil {