refactor: id-keyed popover/context-menu API (cce-ui Phase 6bc slice 2)

register_popover takes &mut; active_popovers holds WidgetIds resolved
through ui_context.tree; context_menu::mouse_input takes the ctx.

 src/main.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index e58ad43..0226166 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -397,7 +397,7 @@ impl Application for TextEditorApp {
         // registry fed the engine's render-only xdg popup, which this app no longer uses.
         self.ui_context.clear_popovers();
         if self.menu_dropdown.popover_rect().is_some() {
-            self.ui_context.register_popover(&self.menu_dropdown);
+            self.ui_context.register_popover(&mut self.menu_dropdown);
         }
 
         use cce_ui::scene::layout::Rect;