message: Hide "Push Tag" from context menu when there are no default remotes
diff: @@ -525,11 +525,13 @@ void ReferenceView::contextMenuEvent(QContextMenuEvent *event)
  if (ref.isTag()) {
  git::Remote remote = ref.repo().defaultRemote();
  + if (remote.isValid()) {
  menu.addAction(tr("Push Tag to %1").arg(remote.name()),
  [this, ref, view, remote] {
  view->push(remote, ref);
  });
  }
  + }
  if (ref.isRemoteBranch()) {
  menu.addAction(tr("New Local Branch"), [this, ref] {
  