Tests: guy != nullptr randomly failing

[NetSysFire]

Describe the bug

In all listed cases are also some armor display tests failing and this may be related.
This specific random failure appears to be comparatively rare.

Unfortunately I lack the privileges in this repo to search through all workflow logs but I feel like I have seen this before. Can't prove it with additional links though.

Attach save file

• https://github.com/CleverRaven/Cataclysm-DDA/actions/runs/8850367074/job/24304548230?pr=73300#step:17:718
• https://github.com/CleverRaven/Cataclysm-DDA/actions/runs/8908067047/job/24465580062?pr=73432#step:17:814

Steps to reproduce

1. Run tests.
2. Win the rng lottery.
3. Witness above failure.

Expected behavior

guy != nullptr

Screenshots

No response

Versions and configuration

n/a

Additional context

No response

[osuphobia]

https://github.com/CleverRaven/Cataclysm-DDA/actions/runs/8482270578/job/23241203488#step:17:697
I also met this failure before.

[osuphobia]

Ahh, a possibility struck me.

Cataclysm-DDA/tests/npc_test.cpp

Lines 240 to 254 in f401475

	/* Test setup. Player should always be at top-left.
	*
	* U is the player, V is vehicle, # is wall, R is rubble & acid with NPC on it,
	* A is acid with NPC on it, W/M is vehicle & acid with (follower/non-follower) NPC on it,
	* B/C is acid with (follower/non-follower) NPC on it.
	*/
	static constexpr int height = 5, width = 17;
	// NOLINTNEXTLINE(cata-use-mdarray,modernize-avoid-c-arrays)
	static constexpr char setup[height][width + 1] = {
	"U ###############",
	"V #R#AAA#W# # #C#",
	" #A#A#A# #M#B# #",
	" ###AAA#########",
	" ##### ",
	};

The test case check_npc_movement is checking if NPC escapes from dangerous terrains.
W/M is vehicle & acid with (follower/non-follower) NPC on it suggests that you need NPC to spawn in a car.

Cataclysm-DDA/tests/npc_test.cpp

Lines 484 to 491 in f401475

	shared_ptr_fast<npc> guy = make_shared_fast<npc>();
	do {
	guy->normalize();
	guy->randomize();
	// Repeat until we get an NPC vulnerable to acid
	} while( guy->is_immune_field( fd_acid ) );
	guy->spawn_at_precise( tripoint_abs_ms( get_map().getabs( p ) ) );

And it's repeating randomization to get a character vulnerable to acid.
If i guess it right, it is a randomized character that is too big/tall to stay in the car?

[NetSysFire]

CC @Qrox, since you appear to have added this back in #25297 and may know whats going on here