TEntityTypeType.isOK letting stuff through

[CyberiaResurrection]

Cf Odata v3 spec:

6 Entity Type Constructs
Entity types are nominal structural types with a key that consists of one or more references to structural properties. An entity type by definition has an independent existence and can be created, updated or deleted independently of any other types. An entity type is the template for an entity: any uniquely identifiable record such as a customer or order.

A key MUST be supplied if and only if the entity type does not specify a base type. The key consists of one or more references to structural properties of the entity type.