Fix JS error when editing a merged PR's title (#30990)

Author: wxiaoguang

templates/repo/issue/view_title.tmpl

@@ -26,9 +26,7 @@
 		</div>
 		<div class="issue-title-buttons">
 			<button class="ui small basic cancel button">{{ctx.Locale.Tr "repo.issues.cancel"}}</button>
-			<button class="ui small primary button"
-							data-update-url="{{$.RepoLink}}/issues/{{.Issue.Index}}/title"
-							{{if .Issue.IsPull}}data-target-update-url="{{$.RepoLink}}/pull/{{.Issue.Index}}/target_branch"{{end}}>
+			<button class="ui small primary button" data-update-url="{{$.RepoLink}}/issues/{{.Issue.Index}}/title">
 				{{ctx.Locale.Tr "repo.issues.save"}}
 			</button>
 		</div>
@@ -77,7 +75,7 @@
 							{{ctx.Locale.Tr "repo.pulls.title_desc" .NumCommits $headHref $baseHref}}
 						</span>
 					{{end}}
-					<span id="pull-desc-editor" class="tw-hidden flex-text-block">
+					<span id="pull-desc-editor" class="tw-hidden flex-text-block" data-target-update-url="{{$.RepoLink}}/pull/{{.Issue.Index}}/target_branch">
 						<div class="ui floating filter dropdown">
 							<div class="ui basic small button tw-mr-0">
 								<span class="text">{{ctx.Locale.Tr "repo.pulls.compare_compare"}}: {{$.HeadTarget}}</span>

web_src/js/features/repo-issue.js

@@ -626,9 +626,12 @@ export function initRepoIssueTitleEdit() {
     showElem(issueTitleDisplay);
     showElem('#pull-desc-display');
   });
+
+  const pullDescEditor = document.querySelector('#pull-desc-editor'); // it may not exist for a merged PR
+  const prTargetUpdateUrl = pullDescEditor?.getAttribute('data-target-update-url');
+
   const editSaveButton = issueTitleEditor.querySelector('.ui.primary.button');
   editSaveButton.addEventListener('click', async () => {
-    const prTargetUpdateUrl = editSaveButton.getAttribute('data-target-update-url');
     const newTitle = issueTitleInput.value.trim();
     try {
       if (newTitle && newTitle !== oldTitle) {