When a table has been evicted from dict_sys and reloaded internally by
InnoDB for FOREIGN KEY processing, statistics may not be initialized,
but nevertheless row_update_cascade_for_mysql() could invoke
dict_stats_update_if_needed(). In that case, we cannot really update
the statistics. For tables that have STATS_PERSISTENT=1 and
STATS_AUTO_RECALC=1, ANALYZE TABLE might have to be executed later.

dict_stats_update_if_needed(): Replace the assertion with
a conditional early return.