A segmentation fault occurs in JOIN::make_sum_func_list() (sql/sql_select.cc:28560)

A segmentation fault occurs in JOIN::make_sum_func_list() (sql/sql_select.cc:28560) due to a missing null pointer check on a SELECT item. When MariaDB processes an aggregation query (SUM, COUNT, etc.), an invalid or null item in the field_list leads to item->type() being called on a null pointer, resulting in a crash. This can be triggered by malformed or corrupted subqueries, allowing a remote authenticated attacker to cause a denial-of-service (DoS).