The function get_primitive_in_translation_space() calls get_primitive() on line src/primitive.c:652, but fails to test whether the value returned is NULL.

This can cause a segmentation fault at line 656 where pointer "primitive" is dereferenced.

I managed to provoke a crash by calling get_hall_number_from_symmetry() with a doubled set of symmetry operations in which every rotation and translation was duplicated.

I could try to come up with a test input, but the fix looks fairly obvious - just handle a failure of get_primitive() correctly.