fix(pages): a second Delete after deleting layers keeps the page

After a click in the Pages list, layers selected since (Select all, say)
took the first Delete, which left nothing selected, so a second Delete
deleted the page. Delete that doesn't take the page now ends the Pages
list's hold on the keyboard.

crates/ui-egui/src/layers_keys_tests.rs

@@ -175,7 +175,14 @@ fn selected_layers_or_a_canvas_press_take_delete_back_from_the_pages_list() {
     key(&mut u, Key::Delete, false);
     assert_eq!(pages(&u), 2);
     assert!(u.app.session.doc().unwrap().node(a).is_none());
+    // Nothing is selected now, but the list gave up the keyboard: a second Delete keeps the page.
+    assert!(u.app.ui.pages_focus.is_none());
+    key(&mut u, Key::Delete, false);
+    assert_eq!(pages(&u), 2, "a second Delete keeps the page");
     // A press on the canvas gives Delete back to it.
+    u.button(row, true);
+    u.button(row, false);
+    assert!(u.app.ui.pages_focus.is_some());
     let p = pos2(900.0, 700.0);
     u.button(p, true);
     u.button(p, false);

crates/ui-egui/src/menus.rs

@@ -124,6 +124,12 @@ pub fn invoke(app: &mut FigApp, id: &str) {
                 crate::layers::delete_page(app, page);
             }
         }
+        // Otherwise the list gives up the keyboard: once Delete has taken layers selected since the
+        // click (Select all, say), a second Delete must not take the page.
+        "edit.delete" if app.ui.pages_focus.is_some() => {
+            app.ui.pages_focus = None;
+            app.run(id, json!({}));
+        }
         "file.open" => app.open_dialog(),
         "plugin.import" => crate::plugins_ui::import_dialog(app),
         "file.import" => app.import_dialog(false),