Error report when skeletal juggernaut is smashing pile-up

DEBUG : vehicle pile-up has negative drag slowdown -2147483648

FUNCTION : int vehicle::slowdown(int) const
FILE : src/vehicle_move.cpp
LINE : 100

------- ./config/debug.log entry:

src/cata_tiles.cpp:614: The tileset you’re using has no ‘unknown’ tile defined!
12:06:25.499 INFO : Loaded tileset: UNDEAD_PEOPLE_BASE
21:33:40.333 ERROR : (error message will follow backtrace)
#0
(dbghelp: @0x620c16[cataclysm-tiles.exe+0x220c16]),
(libbacktrace: Z21debug_write_backtraceRSo+0x56@0x620c16),
(libbacktrace: 0x620c16 [unknown src]:0 [unknown func]),
#1
(dbghelp: @0x6216aa[cataclysm-tiles.exe+0x2216aa]),
(libbacktrace: Z8DebugLog10DebugLevel10DebugClass+0x34a@0x6216aa),
(libbacktrace: 0x6216aa [unknown src]:0 [unknown func]),
#2
(dbghelp: @0x6245f6[cataclysm-tiles.exe+0x2245f6]),
(libbacktrace: Z12realDebugmsgPKcS0_S0_RKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x76@0x6245f6),
(libbacktrace: 0x6245f6 [unknown src]:0 [unknown func]),
#3
(dbghelp: @0xf4f65e[cataclysm-tiles.exe+0xb4f65e]),
(libbacktrace: ZNK7vehicle8slowdownEi+0x51e@0xf4f65e),
(libbacktrace: 0xf4f65e [unknown src]:0 [unknown func]),
#4
(dbghelp: @0xf2cf93[cataclysm-tiles.exe+0xb2cf93]),
(libbacktrace: ZN7vehicle10gain_movesEv+0x193@0xf2cf93),
(libbacktrace: 0xf2cf93 [unknown src]:0 [unknown func]),
#5
(dbghelp: @0x9bf25d[cataclysm-tiles.exe+0x5bf25d]),
(libbacktrace: ZN3map7vehmoveEv+0xed@0x9bf25d),
(libbacktrace: 0x9bf25d [unknown src]:0 [unknown func]),
#6
(dbghelp: @0x740c18[cataclysm-tiles.exe+0x340c18]),
(libbacktrace: ZN4game7do_turnEv+0x658@0x740c18),
(libbacktrace: 0x740c18 [unknown src]:0 [unknown func]),
#7
(dbghelp: IMG_LoadWEBP_RW+0x67a6b8@0x17be938[cataclysm-tiles.exe+0x13be938]),
(libbacktrace: main+0x10e8@0x17be938),
(libbacktrace: 0x17be938 [unknown src]:0 [unknown func]),
#8
(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),
#9
(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),
#10
(dbghelp: BaseThreadInitThunk+0x14@0x7ffda3617bd4[KERNEL32.DLL+0x17bd4]),
(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),
#11
(dbghelp: RtlUserThreadStart+0x21@0x7ffda49cce51[ntdll.dll+0x6ce51]),
(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),
Backtrace emission took 0 seconds.
src/vehicle_move.cpp:100 [int vehicle::slowdown(int) const] vehicle pile-up has negative drag slowdown -2147483648