The issue here was the read_set bitmap was not set for a field which
was used as a reference in an inner select.
We need to make sure that if we are in an inner select and we have
references from outer select then we update the table bitmaps for
such references.

Introduced a function in the class Item_subselect that would
update bitmaps of table for the references within a
subquery that are defined in outer selects.