Return a missing cache with the specified name or null if
such cache does not exist or could not be created on the fly.
Some caches may be created at runtime if the native provider supports
it. If a lookup by name does not yield any result, a subclass gets a chance
to register such a cache at runtime. The returned cache will be automatically
added to this instance.
name - the name of the cache to retrieve
the missing cache or null if no such cache exists or could be