Make sure we don't treat container type objects as if they're actual living containers.

Author: jnthn

src/ops/nqp.ops

@@ -32,7 +32,7 @@ static PMC *KnowHOWAttribute = NULL;
 static PMC * decontainerize(PARROT_INTERP, PMC *var) {
     if (var->vtable->base_type == smo_id) {
         ContainerSpec *spec = STABLE(var)->container_spec;
-        if (spec) {
+        if (spec && REPR(var)->defined(interp, var)) {
             if (!PMC_IS_NULL(spec->value_slot.class_handle)) {
                 /* Just get slot. */
                 return VTABLE_get_attr_keyed(interp, var, spec->value_slot.class_handle,