Fix an uninitialized variable in debug builds

storage/innobase/dict/drop.cc

 /*****************************************************************************
 
-Copyright (c) 2021, MariaDB Corporation.
+Copyright (c) 2021, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -152,7 +152,7 @@ dberr_t trx_t::drop_table(const dict_table_t &table)
   ut_ad(table.n_lock_x_or_s == 1);
   ut_ad(UT_LIST_GET_LEN(table.locks) >= 1);
 #ifdef UNIV_DEBUG
-  bool found_x;
+  bool found_x= false;
   for (lock_t *lock= UT_LIST_GET_FIRST(table.locks); lock;
        lock= UT_LIST_GET_NEXT(un_member.tab_lock.locks, lock))
   {