tools/settings_migrate_group: extract fieldless reference rows by token

Action rows have no field argument, so a referenced action's
literal extraction anchored on an empty field and matched nothing;
the head pattern now adapts.

Author: libretroadmin

tools/settings_migrate_group.py

@@ -218,7 +218,8 @@ def guard_of(text, pat):
     _tail = [r for r in rows if r[2] in ref_tokens]
     _ref_literals = {}
     for _k3, _f3, _t3, _a3 in _tail:
-        _rm3 = re.search(r'[ \t]*SDESC_\w+_ROW(?:_P|_DS|_EX|_LV)?\(\s*%s,\s*%s,(?:[^()]|\((?:[^()]|\([^()]*\))*\))*\),?' % (_f3, _t3), body)
+        _head3 = (r'\s*%s,\s*%s,' % (_f3, _t3)) if _f3 else (r'\s*%s,' % _t3)
+        _rm3 = re.search(r'[ \t]*SDESC_\w+_ROW(?:_P|_DS|_EX|_LV)?\(%s(?:[^()]|\((?:[^()]|\([^()]*\))*\))*\),?' % _head3, body)
         assert _rm3, _t3
         _rl3 = _rm3.group(0).strip()
         for _g3 in reversed(guards.get(_f3 or _t3, ())):