UI: add uiItemMenuFN which frees it's argument

source/blender/editors/interface/interface_layout.c

@@ -1941,8 +1941,11 @@ static uiBut *ui_item_menu(
 	else
 		but = uiDefMenuBut(block, func, arg, name, 0, 0, w, h, tip);
 
-	if (argN) { /* ugly .. */
-		but->poin = (char *)but;
+	if (argN) {
+		/* ugly .. */
+		if (arg != argN) {
+			but->poin = (char *)but;
+		}
 		but->func_argN = argN;
 	}
 
@@ -2078,6 +2081,18 @@ void uiItemMenuF(uiLayout *layout, const char *name, int icon, uiMenuCreateFunc
 	ui_item_menu(layout, name, icon, func, arg, NULL, "", false);
 }
 
+/**
+ * Version of #uiItemMenuF that free's `argN`.
+ */
+void uiItemMenuFN(uiLayout *layout, const char *name, int icon, uiMenuCreateFunc func, void *argN)
+{
+	if (!func)
+		return;
+
+	/* Second 'argN' only ensures it gets freed. */
+	ui_item_menu(layout, name, icon, func, argN, argN, "", false);
+}
+
 typedef struct MenuItemLevel {
 	int opcontext;
 	/* don't use pointers to the strings because python can dynamically