message: Fix null reference attempt on empty repository.
diff: @@ -88,9 +88,13 @@ RemoteDialog::RemoteDialog(Kind kind, RepoView *parent)
  connect(mRefs, &ReferenceList::referenceSelected,
  [this](const git::Reference &ref) {
  + QString value = QString();
  + if (ref.isValid()) {
  QString key = QString("branch.%1.merge").arg(ref.name());
  git::Config config = RepoView::parentView(this)->repo().config();
  - mRemoteRef->setText(config.value<QString>(key));
  + value = config.value<QString>(key);
  + }
  + mRemoteRef->setText(value);
  });
  mRefs->select(repo.head());
  