MDEV-23991 fixup: Initialize the memory

This regression was introduced in
commit afc9d00c66db946c8240fe1fa6b345a3a8b6fec1.
This is a partial backport of
commit 199863d72b7cccaa4c75641c50c45a83b568ab8c from 10.4.

storage/innobase/dict/dict0stats.cc

@@ -2249,6 +2249,9 @@ dict_stats_update_persistent(
 	}
 
 	ut_ad(!dict_index_is_ibuf(index));
+	mutex_enter(&dict_sys->mutex);
+	dict_stats_empty_index(index, false);
+	mutex_exit(&dict_sys->mutex);
 
 	index_stats_t stats = dict_stats_analyze_index(index);