NPE when CTE and subuquery without a WITH clause are pushed together

With a query such as:

WITH qry_0 as /*+ no_inline */ (SELECT e2 AS a1, e1 as str FROM pm1.g1 AS t) select (select e1 from pm1.g1) as x, a1 from qry_0

that is pushed together to the source, the relationalplanner will throw an NPE when pulling up any nested with clauses because there is no with clause assigned to the subquery.