Centralize retained popup closing

src/node_panel_brush.cpp

@@ -623,7 +623,7 @@ void NodePanelBrushPreset::init()
                     break;
                 }
             }
-            popup->destroy();
+            pp::panopainter::close_legacy_popup_overlay(*popup);
         };
     };
     m_btn_import = find<NodeButton>("import");