message: Only display Restore Location menu if there are saved locations
diff: @@ -2452,7 +2452,17 @@ bool TraceWin::graph_render_popupmenu( graph_info_t &gi )
  ImGui::EndMenu();
  }
  - if ( ImGui::BeginMenu( "Restore Location" ) )
  + bool has_saved_locs = false;
  + for ( size_t i = 0; i < m_graph.saved_locs.size(); i++ )
  + {
  + if ( m_graph.saved_locs[ i ].second )
  + {
  + has_saved_locs = true;
  + break;
  + }
  + }
  +
  + if ( has_saved_locs && ImGui::BeginMenu( "Restore Location" ) )
  {
  for ( size_t i = 0; i < m_graph.saved_locs.size(); i++ )
  {
  