MobjSpawn hook has issues

Reposting this screenshot that I was sent, since nobody bothered to share this issue outside of Discord...

changed milestone to %2.2.10

added Bug Lua Regression labels

changed title from MobjSpawn hook has issues with NiGHTS mode to MobjSpawn hook has issues

This happens because of some strange and dare I say, goofy, MT_NULL spawning...

• NiGHTS because of a hack with transfer points.
• GFZ3 because the laser attack hacks P_TryMove with a temporary mobj.
• Canonballs because A_LobShot also does this for some reason.
• Linedef 434 also spawns MT_NULL.

Since the hooklib refactor, hook calls check if a mobj type is not MT_NULL to determine if it's calling a mobj hook, that's why it's a problem now.

mentioned in issue #761 (closed)

mentioned in merge request !1729 (merged)

closed with merge request !1729 (merged)

mentioned in commit d532546e