message: Make sure we don't try to remove tabs when they don't exist
  This was an oversight.
  Fixes
diff: @@ -828,10 +828,12 @@ namespace winrt::TerminalApp::implementation
  void TerminalPage::_RemoveTabViewItem(const MUX::Controls::TabViewItem& tabViewItem)
  {
  uint32_t tabIndexFromControl = 0;
  - _tabView.TabItems().IndexOf(tabViewItem, tabIndexFromControl);
  -
  + if (_tabView.TabItems().IndexOf(tabViewItem, tabIndexFromControl))
  + {
  + // If IndexOf returns true, we've actually got an index
  _RemoveTabViewItemByIndex(tabIndexFromControl);
  }
  + }
  // Method Description:
  // - Removes the tab (both TerminalControl and XAML)
  