message: Another safety
diff: @@ -1446,6 +1446,9 @@ namespace RINGMesh {
  if( current_viewer_type_ == GEOMODEL && current_viewer_ >= i ) {
  current_viewer_-- ;
  }
  + if( geomodels_.empty() ) {
  + current_viewer_type_ = NONE ;
  + }
  }
  ImGui::PopID() ;
  }
  @@ -1469,6 +1472,9 @@ namespace RINGMesh {
  if( current_viewer_type_ == MESH && current_viewer_ >= i ) {
  current_viewer_-- ;
  }
  + if( meshes_.empty() ) {
  + current_viewer_type_ = NONE ;
  + }
  }
  ImGui::PopID() ;
  }
  