Use the right type OID after creating a shell type

Commit a2e35b53 neglected to update the type OID to use further
down in DefineType when TypeShellMake was changed to return
ObjectAddress instead of OID (it got it right in DefineRange, however.)
This resulted in an internal error message being issued when looking up
I/O functions.

Author: Michael Paquier

Also add Asserts() to a couple of other places to ensure that the type
OID being used is as expected.