If the Nazgul's dealt shadow card has no shadow ability printed on the bottom, does the Nazgul's Forced ability trigger? In other words, is flipping the Shadow card considered to be "resolving the shadow effect"?
The rules make a distinction between shadow card and shadow effect:
3. Resolve shadow effect. The active player flips that
enemy’s shadow card faceup and resolves any shadow
effect that card might have.
If a card has no shadow effect, there is no shadow effect to resolve.