fix wont_hit_friend causing segfault

[osuphobia]

Summary

Bugfixes "npc::wont_hit_friend causing segfault"

Purpose of change

Fix #75707

Describe the solution

Prevent calling nullptr ammo_data.

Describe alternatives you've considered

Testing

Bandit firing a crossbow no longer causes segfault.

Additional context

[PatrikLundell]

So, what happens when a bandit wields an empty crossbow? Not crashing is definitely an improvement, but if the bugger just stands around doing nothing it's not a proper solution.

A guess is that it might be possible to test the behavior by giving a companion a crossbow and a single bolt, tell it to guard a position, and then spawn a zombie for it to engage.

The desired behavior should be to fire the bolt and then switch to a melee weapon. A debugger should be used to verify the changed code actually is called.

And, by the way, is this specific to crossbows? What happens when a firearm runs out of ammo?

[osuphobia]

So, what happens when a bandit wields an empty crossbow? Not crashing is definitely an improvement, but if the bugger just stands around doing nothing it's not a proper solution.

A guess is that it might be possible to test the behavior by giving a companion a crossbow and a single bolt, tell it to guard a position, and then spawn a zombie for it to engage.

The desired behavior should be to fire the bolt and then switch to a melee weapon. A debugger should be used to verify the changed code actually is called.

Actually, that's what a NPC will do when the gun ran out of ammo, with or without this patch.

And, by the way, is this specific to crossbows? What happens when a firearm runs out of ammo?

Only crossbows, and the game crashes in this process only when the NPC has spare bolts in their pocket, where npc::wont_hit_friend will be called an extra time in this condtion.

I didn't find a way to deal with the superpower mentioned in #75331, which allows NPCs to reload the crossbow or shoot a revolver several times in one turn.

[ShnitzelX2]

Thanks, this was indeed the problem: in #75297, I did not check for whether the weapon had ammo (my bad), and I assumed that if guns worked, then crossbows would too. I think I did verify that NPC allies wielding guns could run out of ammo, though, so it's weird that only crossbows do this.