Using the class `ExceptionClass` in combination with a deliberate Cartesian
product can lead to bad join orders, for example
```
EVALUATE NONRECURSIVE RELATION:
Completion::TriedControlFlowElement::getAThrownException_dispred#ff(int this, int result) :-
{1} r1 = JOIN Expr::Expr::getType_dispred#ff_10#join_rhs WITH @integral_type#f ON Expr::Expr::getType_dispred#ff_10#join_rhs.<0>=@integral_type#f.<0> OUTPUT FIELDS {Expr::Expr::getType_dispred#ff_10#join_rhs.<1>}
{1} r2 = JOIN r1 WITH @un_op#f ON r1.<0>=@un_op#f.<0> OUTPUT FIELDS {r1.<0>}
{1} r3 = JOIN r2 WITH Stmt::TryStmt::getATriedElement#ff_1#join_rhs ON r2.<0>=Stmt::TryStmt::getATriedElement#ff_1#join_rhs.<0> OUTPUT FIELDS {r2.<0>}
{2} r4 = JOIN r3 WITH Stmt::ExceptionClass#f CARTESIAN PRODUCT OUTPUT FIELDS {Stmt::ExceptionClass#f.<0>,r3.<0>}
{2} r5 = JOIN r4 WITH System::SystemOverflowExceptionClass#class#f ON r4.<0>=System::SystemOverflowExceptionClass#class#f.<0> OUTPUT FIELDS {r4.<1>,r4.<0>}
```
where the CP is made with `ExceptionClass` rather than `SystemOverflowExceptionClass`
directly.
