Raise exception when a Designate's OCDREF points to non-existing OCD

Currently, if a Designate's OCDREF references to a non-existing OCD, the MTI implementation simply ignores it.
The result of this behavior is that the following code returns null both when (1) the designate ID is not defined in the meta-data, (2) the designate points to an invalid OCD:

ObjectClassDefinition objClassDef =
metaTypeInformation.getObjectClassDefinition(designateId, locale);

It is my understanding from the spec that the latter situation should be treated as an exception.

Thanks