Game crash on finishing/accepting next ranch mission

Game version: 0.D-11170-g64b5e04

Operating system: Windows 10

Tiles or curses: Default

Mods active:

### Expected behavior
Finish 5 backpacks delivery and end conversation

### Actual behavior
The game crashes when I end the conversation after finishing the backpack mission at the Ranch

### Steps to reproduce the behavior
Finish the backpack mission and end the conversation

Crash Log:

```
The program has crashed.
See the log file for a stack trace.
CRASH LOG FILE: ./config/crash.log
VERSION: 0.D-11170-g64b5e04
TYPE: Signal
MESSAGE: SIGSEGV: Segmentation fault
STACK TRACE:

#0
(dbghelp: @0x5f84a6[cataclysm-tiles.exe+0x1f84a6]),
(libbacktrace: Z21debug_write_backtraceRSo+0x56@0x5f84a6),
(libbacktrace: 0x5f84a6 [unknown src]:0 [unknown func]),
#1
(dbghelp: @0x5de7ef[cataclysm-tiles.exe+0x1de7ef]),
(libbacktrace: log_crash+0x4af@0x5de7ef),
(libbacktrace: 0x5de7ef [unknown src]:0 [unknown func]),
#2
(dbghelp: @0x5df4b2[cataclysm-tiles.exe+0x1df4b2]),
(libbacktrace: signal_handler+0x32@0x5df4b2),
(libbacktrace: 0x5df4b2 [unknown src]:0 [unknown func]),
#3
(dbghelp: SMPEG_error+0x4b034@0xff1a80[cataclysm-tiles.exe+0xbf1a80]),
(libbacktrace: gnu_exception_handler+0x70@0xff1a80),
(libbacktrace: 0xff1a80 /home/narc/src/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-5.4.0.build_/mingw-w64-v5.0.2/mingw-w64-crt/crt/crt_handler.c:223 _gnu_exception_handler),
#4
(dbghelp: _C_specific_handler+0x98@0x7ffdfa1d8068[msvcrt.dll+0x28068]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
#5
(dbghelp: _chkstk+0x11f@0x7ffdfc32477f[ntdll.dll+0xa477f]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
#6
(dbghelp: RtlWalkFrameChain+0x14bf@0x7ffdfc284bef[ntdll.dll+0x4bef]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
#7
(dbghelp: KiUserExceptionDispatcher+0x2e@0x7ffdfc3234ee[ntdll.dll+0xa34ee]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
#8
(dbghelp: @0x961753[cataclysm-tiles.exe+0x561753]),
(libbacktrace: ZN3map20add_vehicle_to_cacheEP7vehicle+0x93@0x961753),
(libbacktrace: 0x961753 [unknown src]:0 [unknown func]),
#9
(dbghelp: @0x9619dc[cataclysm-tiles.exe+0x5619dc]),
(libbacktrace: ZN3map19reset_vehicle_cacheEi+0x4c@0x9619dc),
(libbacktrace: 0x9619dc [unknown src]:0 [unknown func]),
#10
(dbghelp: @0x6c8005[cataclysm-tiles.exe+0x2c8005]),
(libbacktrace: ZN4game11refresh_allEv+0x35@0x6c8005),
(libbacktrace: 0x6c8005 [unknown src]:0 [unknown func]),
#11
(dbghelp: @0xbf9d75[cataclysm-tiles.exe+0x7f9d75]),
(libbacktrace: ZN11npc_trading5tradeER3npciRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x1e5@0xbf9d75),
(libbacktrace: 0xbf9d75 [unknown src]:0 [unknown func]),
#12
(dbghelp: @0xbecb59[cataclysm-tiles.exe+0x7ecb59]),
(libbacktrace: ZN13talk_function14mission_rewardER3npc+0x49@0xbecb59),
(libbacktrace: 0xbecb59 [unknown src]:0 [unknown func]),
#13
(dbghelp: @0xbcbaa5[cataclysm-tiles.exe+0x7cbaa5]),
(libbacktrace: ZNK13talk_effect_t5applyER8dialogue+0x45@0xbcbaa5),
(libbacktrace: 0xbcbaa5 [unknown src]:0 [unknown func]),
#14
(dbghelp: @0xbe4ff8[cataclysm-tiles.exe+0x7e4ff8]),
(libbacktrace: ZN8dialogue3optER15dialogue_windowRK10talk_topic+0x758@0xbe4ff8),
(libbacktrace: 0xbe4ff8 [unknown src]:0 [unknown func]),
#15
(dbghelp: @0xbe5dec[cataclysm-tiles.exe+0x7e5dec]),
(libbacktrace: ZN3npc9talk_to_uEbb+0x7fc@0xbe5dec),
(libbacktrace: 0xbe5dec [unknown src]:0 [unknown func]),
#16
(dbghelp: @0xbe8096[cataclysm-tiles.exe+0x7e8096]),
(libbacktrace: ZN4game4chatEv+0x786@0xbe8096),
(libbacktrace: 0xbe8096 [unknown src]:0 [unknown func]),
#17
(dbghelp: @0x747240[cataclysm-tiles.exe+0x347240]),
(libbacktrace: ZN4game13handle_actionEv+0x2420@0x747240),
(libbacktrace: 0x747240 [unknown src]:0 [unknown func]),
#18
(dbghelp: @0x710a4d[cataclysm-tiles.exe+0x310a4d]),
(libbacktrace: ZN4game7do_turnEv+0x72d@0x710a4d),
(libbacktrace: 0x710a4d [unknown src]:0 [unknown func]),
#19
(dbghelp: IMG_LoadWEBP_RW+0x65903c@0x173c92c[cataclysm-tiles.exe+0x133c92c]),
(libbacktrace: main+0x10fc@0x173c92c),
(libbacktrace: 0x173c92c [unknown src]:0 [unknown func]),
#20
(dbghelp: @0x4013ed[cataclysm-tiles.exe+0x13ed]),
(libbacktrace: _tmainCRTStartup+0x23d@0x4013ed),
(libbacktrace: 0x4013ed /home/narc/src/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-5.4.0.build_/mingw-w64-v5.0.2/mingw-w64-crt/crt/crtexe.c:336 __tmainCRTStartup),
#21
(dbghelp: @0x4014fb[cataclysm-tiles.exe+0x14fb]),
(libbacktrace: WinMainCRTStartup+0x1b@0x4014fb),
(libbacktrace: 0x4014fb /home/narc/src/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-5.4.0.build_/mingw-w64-v5.0.2/mingw-w64-crt/crt/crtexe.c:186 WinMainCRTStartup),
#22
(dbghelp: BaseThreadInitThunk+0x14@0x7ffdf9ad7974[KERNEL32.DLL+0x17974]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
#23
(dbghelp: RtlUserThreadStart+0x21@0x7ffdfc2ea271[ntdll.dll+0x6a271]),
(backtrace_syminfo failed: errno = -1, msg = no symbol table in PE/COFF executable),
(backtrace_pcinfo failed: errno = -1, msg = no debug info in PE/COFF executable),
```

Start by reproducing the Ranch backpack mission on the reported Windows build and inspect the stack trace from talk_function::mission_reward through npc_trading::trade, game::refresh_all, and map vehicle-cache handling. Trace the crash to its source location, add a regression test if the relevant test area is identifiable, and verify that completing the mission no longer crashes when the conversation ends.

Written by the indexing model from the issue text.