write_flif segfaults

[dniku]

import pyflif
import numpy as np

img = np.random.randint(0, 255, size=(320, 240, 3), dtype=np.uint8)
pyflif.write_flif('/tmp/test.flif', img)

causes CPython to segfault with the following backtrace (obtained with gdb --args python test.py):

#0  0x00007fffe3efa1e5 in FLIF_ENCODER::transformations(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&) () from /usr/lib/libflif.so.0
#1  0x00007fffe3effecc in FLIF_ENCODER::encode_file(char const*) () from /usr/lib/libflif.so.0
#2  0x00007fffe3efff8a in flif_encoder_encode_file () from /usr/lib/libflif.so.0
#3  0x00007ffff7f816d0 in ffi_call_unix64 () from /usr/lib/libffi.so.6
#4  0x00007ffff7f810a0 in ffi_call () from /usr/lib/libffi.so.6
#5  0x00007ffff7329625 in _ctypes_callproc () from /usr/lib/python3.7/lib-dynload/_ctypes.cpython-37m-x86_64-linux-gnu.so
#6  0x00007ffff7329fb0 in ?? () from /usr/lib/python3.7/lib-dynload/_ctypes.cpython-37m-x86_64-linux-gnu.so
#7  0x00007ffff7b9c62c in _PyObject_FastCallKeywords () from /usr/lib/libpython3.7m.so.1.0
#8  0x00007ffff7be10db in _PyEval_EvalFrameDefault () from /usr/lib/libpython3.7m.so.1.0
#9  0x00007ffff7b6f6db in _PyFunction_FastCallKeywords () from /usr/lib/libpython3.7m.so.1.0
#10 0x00007ffff7bdc032 in _PyEval_EvalFrameDefault () from /usr/lib/libpython3.7m.so.1.0
#11 0x00007ffff7b29dbb in _PyFunction_FastCallDict () from /usr/lib/libpython3.7m.so.1.0
#12 0x00007ffff7b39818 in _PyObject_Call_Prepend () from /usr/lib/libpython3.7m.so.1.0
#13 0x00007ffff7b286a2 in _PyObject_FastCallDict () from /usr/lib/libpython3.7m.so.1.0
#14 0x00007ffff7bddae7 in _PyEval_EvalFrameDefault () from /usr/lib/libpython3.7m.so.1.0
#15 0x00007ffff7b6f6db in _PyFunction_FastCallKeywords () from /usr/lib/libpython3.7m.so.1.0
#16 0x00007ffff7be06ea in _PyEval_EvalFrameDefault () from /usr/lib/libpython3.7m.so.1.0
#17 0x00007ffff7b28d09 in _PyEval_EvalCodeWithName () from /usr/lib/libpython3.7m.so.1.0
#18 0x00007ffff7b29c64 in PyEval_EvalCodeEx () from /usr/lib/libpython3.7m.so.1.0
#19 0x00007ffff7b29c8c in PyEval_EvalCode () from /usr/lib/libpython3.7m.so.1.0
#20 0x00007ffff7c52694 in ?? () from /usr/lib/libpython3.7m.so.1.0
#21 0x00007ffff7c53b6e in PyRun_FileExFlags () from /usr/lib/libpython3.7m.so.1.0
#22 0x00007ffff7c57035 in PyRun_SimpleFileExFlags () from /usr/lib/libpython3.7m.so.1.0
#23 0x00007ffff7c592a7 in ?? () from /usr/lib/libpython3.7m.so.1.0
#24 0x00007ffff7c594ec in _Py_UnixMain () from /usr/lib/libpython3.7m.so.1.0
#25 0x00007ffff7db6ce3 in __libc_start_main () from /usr/lib/libc.so.6
#26 0x000055555555505e in _start ()