Type validation error as ReduceExpressionRule fails to preserve type nullability

  @Test public <T> void testReduceCaseNullabilityChange() throws Exception {
    HepProgram program = new HepProgramBuilder()
        .addRuleInstance(ReduceExpressionsRule.FILTER_INSTANCE)
        .addRuleInstance(ReduceExpressionsRule.PROJECT_INSTANCE)
        .build();

    try (Hook.Closeable a = Hook.REL_BUILDER_SIMPLIFY.add(Hook.propertyJ(false))) {
      checkPlanning(program,
          "select case when empno = 1 then 1 when 1 IS NOT NULL then 2 else null end as qx "
              + "from emp");
    }