Cutscene Crash When Attacking with Trebuchet

Using the Attack option in Cutscene Editor with a trebuchet as the attacker will reliably crash the game.

To replicate:

1. Create a cutscene with a trebuchet and a target.
2. Add "Attack" command with trebuchet as attacker, same grid location, and target as target.
3. Playback. The attack animation will play, then following error occurs.

Misc. things:

• Delay before attack animation does not prevent crash.
• Location of target does not prevent crash.
• Ballista does not have the same issue
• Other factions' trebuchets should have the same issue (only tested with Cherrystone and Heavensong)