Prevent segfault when target of firstaid_activity_actor disappears

[inogenous]

Summary

Bugfixes "Prevent segfault when target of firstaid_activity_actor disappears"

Purpose of change

Prevents segfault when performing firstaid_activity_actor but the bandage tool disappeared. Fixes #75309 .

Describe the solution

Backtrace of fixed segfault:

Thread 1 "cataclysm-tiles" received signal SIGSEGV, Segmentation fault.
(gdb) bt
 #0  0x0000555555ece5a4 in item::get_usable_item_helper<item> (use_name="heal", self=...) at src/item.cpp:11584
 #1  item::get_usable_item (this=0x0, use_name="heal") at src/item.cpp:11606
 #2  0x000055555599c6bf in firstaid_activity_actor::finish (this=0x55559b583f20, act=..., who=...) at src/activity_actor.cpp:6651
 #3  0x00005555564d8c6b in player_activity::do_turn (this=0x555558108218, you=...) at src/player_activity.cpp:391
 #4  0x0000555555ce3fa6 in do_turn () at src/do_turn.cpp:532
 #5  0x000055555577511a in main (argc=<optimized out>, argv=<optimized out>) at src/main.cpp:873

An example where this happened was when the bandage was inside a spillable container (clay canning pot), that spilled its contents when starting the activity. Spiling the clay canning pot invalidates the item_location. Backtrace of when the clay canning pot was spilled:

 #0  item_pocket::get_name (this=0x555557fa7540) at src/item_pocket.cpp:2117
 #1  item_pocket::handle_liquid_or_spill (this=this@entry=0x555557fa7540, guy=..., avoid=0x555557fa8060) at src/item_pocket.cpp:806
 #2  0x0000555555a6aa60 in avatar_action::use_item (you=..., loc=..., method="heal") at src/avatar_action.cpp:1212
 #3  0x0000555555a6dda7 in avatar_action::eat_or_use (you=..., loc=...) at src/avatar_action.cpp:988
 #4  0x0000555555e3e1c5 in game::do_regular_action (this=this@entry=0x555557f94a60, act=@0x7fffffffd1b0: ACTION_EAT, player_character=..., mouse_target=std::optional [no contained value]) at src/handle_action.cpp:2479
 #5  0x0000555555e41260 in game::handle_action (this=0x555557f94a60) at src/handle_action.cpp:3176
 #6  0x0000555555ce422f in do_turn () at /usr/include/c++/13/bits/unique_ptr.h:199
 #7  0x000055555577511a in main (argc=<optimized out>, argv=<optimized out>) at src/main.cpp:873

Describe alternatives you've considered

Having the bandages inside the clay canning pot like that should not be possible since the clay canning pot is a spillable container, but apparently it is, and that's possibly a separate issue. Wielding the clay canning pot should be ok, since that wouldnt spill it, but having it inside the inventory like that causes the issue. Maybe autopickup placed them inside the spillable container? It's possibly a separate issue to prevent this in the first place.

Testing

When performing the steps in #75309 , the segfault can longer be reproduced. Instead, it shows the debugmsg "Lost tool used for healing".

Additional context

[Escamado]

I would never have guessed the canning pot was causing it, thats amazing, thank you so much for sporting it!!!

[Escamado]

Also for the canning pot in my inventory , its the pack frame that lets you strap a single big container item, in this case the canning pot I was using as a makeshift backpack.

[RenechCDDA]

@inogenous Looks like this could use a backport, #75689 appears to have the same stack trace on a 0.H release candidate?

[inogenous]

Awesome, thanks @RenechCDDA for the ping! Have backported the change in #75691 .