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);

src/platform/platform_win32.cpp

@@ -86,7 +86,8 @@ static LRESULT CALLBACK win32_wndproc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM
             pw->should_close = true;
         return 0;
     case WM_DESTROY:
-        PostQuitMessage(0);
+        if (pw == g_main_window)
+            PostQuitMessage(0);
         return 0;
     case WM_SYSCOMMAND:
         if ((wparam & 0xfff0) == SC_KEYMENU)

src/ui/ui_popups.cpp

@@ -80,11 +80,12 @@ void popup_close(PopupWindow *popup) {
     if (popup->open_flag)
         *popup->open_flag = 0;
 
+    popup->alive = 0;
+    platform_set_frame_callback(popup->platform_window, nullptr, nullptr);
+
     ui_destroy(popup->ui_ctx);
     renderer_destroy(popup->renderer);
     platform_destroy_window(popup->platform_window);
-
-    popup->alive = 0;
 }
 
 void popup_do_frame(PopupWindow *popup, F32 dt) {