message: Fix showing a dialog multiple times
  After the dialog is displayed, always clear it out. If we don't, we won't be able to display another!
  * regressed in
  * [x] Fixes
diff: @@ -348,7 +348,11 @@ namespace winrt::TerminalApp::implementation
  }
  _dialog = dialog;
  -
  + // GH#12622: After the dialog is displayed, always clear it out. If we
  + // don't, we won't be able to display another!
  + const auto cleanup = wil::scope_exit([this]() {
  + _dialog = nullptr;
  + });
  // IMPORTANT: This is necessary as documented in the ContentDialog MSDN docs.
  // Since we're hosting the dialog in a Xaml island, we need to connect it to the
  // xaml tree somehow.
  