To see the issue:

1. Add a mob to the mob spawn blacklist while using OpenBlocks 1.2.0.

2. Start the game and give yourself a spawn egg.

3. Observer that, when using the spawn egg, the mob immediately despawns, as it has been caught by the blacklist.

4. Add a mob to the mob spawn blacklist while using OpenBlocks 1.2.2.

5. Start the game and give yourself a spawn egg.

6. Observer that, when using the spawn egg, the mob spawns successfully and does not despawn. The same mob can also be observed spawning naturally in the world.

This was dropped when ghosts were.
I'll leave this issue here, we should really add this back.

It was accidental droppage.

I'm too tired to add it back :(

It's okay Mikee :)
That's why you've got us.

This is fixed