Indexmanager seems to get into inconsistent state when trying to define an index on a nonexistent nodeType

When trying to register an index on a nonexistent nodeType a NPE is triggered from RepositoryIndexManager Line 795 in 4.0 branch.

                    for (String typeAndSubtype : subtypesByName.get(nodeTypeName)) {

That alone is no bug, but after that the IndexManager keeps throwing NPE's when registering new Indexes or even trying to access it.