LINQ subqueries wrongly altered by SelectClauseVisitor

[bahusoid]

SelectClauseVisitor modifies select clause for retrieval adding post processing lambdas SelectClauseVisitor.ProjectionExpression that are never executed for subqueries.

For instance, the following select expression a.Name ?? "Test" is transformed simply to a.Name with post processing lambda (result) => result ?? "Test". Such lambdas are simply ignored for subqueries executing modified query with different logic.

It seems a very old bug but let's fix in 5.4