menu_setting: stop clobbering SD_FREE_FLAG_MAIN_MENU_GROUP in setting_group_setting

setting_group_setting() sets SD_FREE_FLAG_MAIN_MENU_GROUP on top-level
ST_GROUP settings whose parent is the main menu, but a leftover blanket
"result.free_flags = 0;" a few lines below the OR-assignment wiped the
bit back out on every group. result is already zero-initialised via
"result = {0}", so the reset was redundant as well as destructive.

With the flag never surviving, menu_cbs_title.c did not bind
action_get_title_group_settings for the main-menu/tab entries, so their
titles fell through to action_get_title_default ("Select File") on XMB,
GLUI and Ozone. The same flag gates menu_cbs_left.c / menu_cbs_right.c,
so left/right handling on those entries was silently affected too.

Fixes #19180.

Author: LibretroAdmin

menu/menu_setting.c

@@ -1451,8 +1451,10 @@ static rarch_setting_t setting_group_setting(
    result.max                       = 0.0;
 
    result.flags                     = 0;
-   result.free_flags                = 0;
-
+   /* Note: free_flags is already zero-initialised by 'result = {0}'
+    * above; do not reset it here, or the SD_FREE_FLAG_MAIN_MENU_GROUP
+    * bit set for top-level groups gets clobbered (breaks the main-menu
+    * / tab titles, left/right handlers). */
 
    result.bind_type                 = 0;
    result.browser_selection_type    = ST_NONE;