Prefer stored title over GTK label in SetIcon

Updated MenuItem::SetIcon to use the stored title if available when preserving the label text, falling back to the GTK widget label only if the title is not set. This ensures consistency when the title is managed internally.

Author: lijy91

src/platform/linux/menu_linux.cpp

@@ -276,9 +276,15 @@ void MenuItem::SetIcon(std::shared_ptr<Image> image) {
     return;
   }
 
-  // Get current label text to preserve it
-  const char* label_text = gtk_menu_item_get_label(GTK_MENU_ITEM(pimpl_->gtk_menu_item_));
-  std::string current_label = label_text ? label_text : "";
+  // Get current label text to preserve it - prefer stored title over GTK widget
+  std::string current_label;
+  if (pimpl_->title_.has_value()) {
+    current_label = pimpl_->title_.value();
+  } else {
+    // Fallback to GTK widget if title not set
+    const char* label_text = gtk_menu_item_get_label(GTK_MENU_ITEM(pimpl_->gtk_menu_item_));
+    current_label = label_text ? label_text : "";
+  }
 
   // Remove existing child widget
   GtkWidget* existing_child = gtk_bin_get_child(GTK_BIN(pimpl_->gtk_menu_item_));