Use TObjPtr to improve null checking. Add option to clear only specific kinds of Behaviors. Fixed removal checks while ticking. Don't stop at now-null behaviors when iterating.
Imported Behaviors to the engine to allow them to properly clean up their level list. Restrict Behaviors from being new'd in ZScript as they need an owner to function.
Allows for arbitrary behaviors to be attached to Actors in a way that doesn't require the use of Inventory tokens. This list can't be freely modified nor can it have duplicates meaning it has far better deterministic behavior than using Inventory items for this purpose.
Bogus pointers and offsets were serialized silently
This will to find other cases of dangling pointers, and protect from loading of broken saved games
https://forum.zdoom.org/viewtopic.php?t=67494
