fix(AGraph): unref transient GtkBuilder on all menu-build paths

The GtkBuilder created for menu construction was never unref'd on any
path (success or throw), leaking one builder per graph module with a
menu. Unref on each throw and at the end, and take an explicit ref on
menu_ so it survives dropping the builder (mirrors ALabel).

src/AGraph.cpp

@@ -79,13 +79,17 @@ AGraph::AGraph(const Json::Value& config, const std::string& name, const std::st
 
       // Make the GtkBuilder and check for errors in his parsing
       if (gtk_builder_add_from_string(builder, fileContent.str().c_str(), -1, nullptr) == 0U) {
+        g_object_unref(builder);
         throw std::runtime_error("Error found in the file " + menuFile);
       }
 
       menu_ = gtk_builder_get_object(builder, "menu");
       if (menu_ == nullptr) {
+        g_object_unref(builder);
         throw std::runtime_error("Failed to get 'menu' object from GtkBuilder");
       }
+      // Keep the menu alive after dropping the transient GtkBuilder.
+      g_object_ref(menu_);
       submenus_ = std::map<std::string, GtkMenuItem*>();
       menuActionsMap_ = std::map<std::string, std::string>();
 
@@ -98,6 +102,7 @@ AGraph::AGraph(const Json::Value& config, const std::string& name, const std::st
         g_signal_connect(submenus_[key], "activate", G_CALLBACK(handleGtkMenuEvent),
                          (gpointer)menuActionsMap_[key].c_str());
       }
+      g_object_unref(builder);
     } catch (std::runtime_error& e) {
       spdlog::warn("Error while creating the menu : {}. Menu popup not activated.", e.what());
     }