MDEV-16230: Server crashes when Analyze format=json is run with a window function with empty PARTITION BY and ORDER BY clauses

Currently when both PARTITION BY and ORDER BY clauses are empty then we create a Item
with the first field in the select list and sort with that field.
It should be created as an Item_temptable_field instead of Item_field because the
print() function continues to work even if the table has been dropped.