Comment 24 for bug 1690519

Another one:

Thread 1 "widelands" received signal SIGSEGV, Segmentation fault.
0x0000000000c5818c in std::__atomic_base<int>::fetch_sub (__m=std::memory_order_acq_rel, __i=1, this=0x10b714978)
    at /usr/include/c++/6.3.1/bits/atomic_base.h:524
524 { return __atomic_fetch_sub(&_M_i, __i, __m); }

Backtrace attached.