message: Disable `update-pr-from-base-branch` when action is impossible
diff: @@ -69,6 +69,10 @@ async function addButton(): Promise<void> {
  const {base, head} = getBranches();
  + if (head === 'unknown repository') {
  + return;
  + }
  +
  // Draft PRs already have this info on the page
  const [outOfDateContainer] = select.all('.completeness-indicator-problem + .status-heading')
  .filter(title => (title.textContent!).includes('out-of-date'));
  