This patch corrects the fix for MDEV-32569. The latter has not taken into
account the fact not each statement uses the SELECT_LEX structure. In
particular CALL statements do not use such structure. However the parameter
passed to the stored procedure used in such a statement may require an
invocation of Type_std_attributes::agg_item_set_converter().

Approved by Oleksandr Byelkin <sanja@mariadb.com>