fix crash when closing platform popups

src/main.cpp

@@ -1919,12 +1919,16 @@ static void do_frame(AppState *app) {
     }
 
     ui_widgets_begin_frame(input);
-    if (app->master_layout == 0) ui_piano_update_input(&app->piano_state);
-    update_panel_splitters(app);
 
     // Build UI with Clay
     ui_begin_frame(app->ui, (F32)w, (F32)h, input.mouse_pos, input.mouse_down,
                    input.scroll_delta, dt);
+
+    // These query previous frame's Clay layout data (Clay_GetElementData,
+    // Clay_PointerOver) so they must run after ui_begin_frame sets the context.
+    if (app->master_layout == 0) ui_piano_update_input(&app->piano_state);
+    update_panel_splitters(app);
+
     build_ui(app);
     Clay_RenderCommandArray render_commands = ui_end_frame(app->ui);
 
@@ -2078,6 +2082,7 @@ int main(int argc, char **argv) {
     }
 
     popup_close_all();
+    platform_set_frame_callback(window, nullptr, nullptr);
     audio_destroy(audio);
     midi_destroy(midi);
     ui_destroy(ui);