message: Fix console error in `mark-unread` on non-conversation views
diff: @@ -412,8 +412,10 @@ async function init(): Promise<void> {
  } else if (pageDetect.isPR() || pageDetect.isIssue()) {
  await markRead(location.href);
  + if (pageDetect.isPRConversation() || pageDetect.isIssue()) {
  addMarkUnreadButton();
  onUpdatableContentUpdate(select('#partial-discussion-sidebar')!, addMarkUnreadButton);
  + }
  } else if (pageDetect.isDiscussionList()) {
  for (const discussion of await getNotifications()) {
  const {pathname} = new URL(discussion.url);
  