Bug report | Arithmetical error

The program has crashed.
See the log file for a stack trace.
CRASH LOG FILE: ./config/crash.log
VERSION: 0.D
TYPE: Signal
MESSAGE: SIGFPE: Arithmetical error
STACK TRACE:

./cataclysm-tiles(_Z21debug_write_backtraceRSo+0x25) [0x841ee6]
./cataclysm-tiles() [0x8344d7]
./cataclysm-tiles() [0x8346d8]
/usr/lib/libc.so.6(+0x3a7e0) [0x7fd47a8027e0]
./cataclysm-tiles(_ZN12defense_game10spawn_waveEv+0x149) [0x850821]
./cataclysm-tiles(_ZN4game7do_turnEv+0x3d) [0x8e03f5]
./cataclysm-tiles(main+0x1483) [0x6b29f5]
/usr/lib/libc.so.6(__libc_start_main+0xf3) [0x7fd47a7eeee3]
./cataclysm-tiles(_start+0x29) [0x6d8849]

Attempting to repeat stack trace using debug symbols...
debug_write_backtrace(std::ostream&)
??:?
log_crash
crash.cpp:?
signal_handler
crash.cpp:?
??
??:0
defense_game::spawn_wave()
??:?
game::do_turn()
??:?
main
??:?
??
??:0
_start
??:?

Defense mod was not touched in a long time.