Fix intermittent panic in notify issue change content (#23019)

Ensure that issue pullrequests are loaded before trying to set the
self-reference.

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <leon@kske.dev>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

models/issues/issue.go

@@ -251,13 +251,15 @@ func (issue *Issue) LoadPoster(ctx context.Context) (err error) {
 
 // LoadPullRequest loads pull request info
 func (issue *Issue) LoadPullRequest(ctx context.Context) (err error) {
-	if issue.IsPull && issue.PullRequest == nil {
-		issue.PullRequest, err = GetPullRequestByIssueID(ctx, issue.ID)
-		if err != nil {
-			if IsErrPullRequestNotExist(err) {
-				return err
+	if issue.IsPull {
+		if issue.PullRequest == nil {
+			issue.PullRequest, err = GetPullRequestByIssueID(ctx, issue.ID)
+			if err != nil {
+				if IsErrPullRequestNotExist(err) {
+					return err
+				}
+				return fmt.Errorf("getPullRequestByIssueID [%d]: %w", issue.ID, err)
 			}
-			return fmt.Errorf("getPullRequestByIssueID [%d]: %w", issue.ID, err)
 		}
 		issue.PullRequest.Issue = issue
 	}

services/webhook/notifier.go

@@ -150,7 +150,6 @@ func (m *webhookNotifier) NotifyIssueChangeAssignee(ctx context.Context, doer *u
 			log.Error("LoadPullRequest failed: %v", err)
 			return
 		}
-		issue.PullRequest.Issue = issue
 		apiPullRequest := &api.PullRequestPayload{
 			Index:       issue.Index,
 			PullRequest: convert.ToAPIPullRequest(ctx, issue.PullRequest, nil),
@@ -196,7 +195,6 @@ func (m *webhookNotifier) NotifyIssueChangeTitle(ctx context.Context, doer *user
 			log.Error("LoadPullRequest failed: %v", err)
 			return
 		}
-		issue.PullRequest.Issue = issue
 		err = PrepareWebhooks(ctx, EventSource{Repository: issue.Repo}, webhook_module.HookEventPullRequest, &api.PullRequestPayload{
 			Action: api.HookIssueEdited,
 			Index:  issue.Index,
@@ -328,7 +326,10 @@ func (m *webhookNotifier) NotifyIssueChangeContent(ctx context.Context, doer *us
 	mode, _ := access_model.AccessLevel(ctx, issue.Poster, issue.Repo)
 	var err error
 	if issue.IsPull {
-		issue.PullRequest.Issue = issue
+		if err := issue.LoadPullRequest(ctx); err != nil {
+			log.Error("LoadPullRequest: %v", err)
+			return
+		}
 		err = PrepareWebhooks(ctx, EventSource{Repository: issue.Repo}, webhook_module.HookEventPullRequest, &api.PullRequestPayload{
 			Action: api.HookIssueEdited,
 			Index:  issue.Index,