MDEV-25951 followup: Add #ifdef around debug code

storage/innobase/dict/dict0load.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2016, 2020, MariaDB Corporation.
+Copyright (c) 2016, 2021, 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
@@ -2577,6 +2577,7 @@ dict_load_indexes(
 				goto func_exit;
 			}
 
+#ifdef UNIV_DEBUG
 			// The following assertion doesn't hold for FTS indexes
 			// as it may have prefix_len=1 with any charset
 			if (index->type != DICT_FTS) {
@@ -2587,6 +2588,7 @@ dict_load_indexes(
 					      % f.col->mbmaxlen == 0);
 				}
 			}
+#endif /* UNIV_DEBUG */
 		}
 next_rec:
 		btr_pcur_move_to_next_user_rec(&pcur, &mtr);