Aiming at creatures can cause segfaults

[Coolthulhu]

• Spawn a shotgun, load it with shot
• Remove vision-enhancing items and mutations
• Set the time to night (23 hour)
• Spawn a shocker in range
• Aim at it until it moves
• Segfault

Doesn't reproduce 100% reliably, but is still rather easy to reproduce. May require killing all critters first as there is a high chance it's index-dependent.
Could be related to the critter moving out of range, hence shotgun.

EDIT: Pinging @mugling who authored the most recent aiming PR and thus is the most likely to know what is causing this.
Forum thread:
http://smf.cataclysmdda.com/index.php?topic=13016.0

[BruceHoss]

Problem related to report #17813.

[mugling]

Pinging @mugling who authored the most recent aiming PR

PR was #17767

Does anyone have a stacktrace?

[mugling]

Can reproduce

do_aim (p=0x8051d7600, t=@0x7fffffff4ce0, target=@0x7fffffff4cdc, relevant=0x8051d78f0, tpos=@0x7fffffff4cf8)
    at src/ranged.cpp:943
943     if( t[target]->pos() != tpos ) {