Analysis:
This bug is yet another incarnation of the generic problem
where optimization of the outer query triggers evaluation
of a subquery, and this evaluation performs a destructive
change to the subquery plan. Specifically a temp table is
created for the DISTINCT operation that replaces the
original subquery table. Later, select_describe() attempts
to print the table name, however, there is no corresponding
TABLE_LIST object to the internal temp table, so we get a
crash. Execution works fine because it is not interested in
the corresponding TABLE_LIST object (or its name).

Solution:
Similar to other such bugs, block the evaluation of expensive
Items in convert_const_to_int().