Fix exception when binding incomplete subselects
Fix exception when binding incomplete subselects

It's possible that the binder is asked to bind a subselect that doesn't
have any columns. This can happen in cases like this:

   SELECT  (SELECT * FROM
   FROM EmployeeTerritories et

In those cases we shouldn't report an error but we can't return bound
single row subselect either.

terrajobst/nquery-vnext