(flatten nil) seg faults about ferret

[kiranshila]

It looks like the problem comes from seqable? as that seg faults for nil.

Your unit test only test one case?

(deftest seqable?-test
  (is (seqable? (list 1 2 3))))

[kiranshila]

Ok so the problem is the overloaded call to cast

inline seekable_i* var::cast<seekable_i>() const { return obj->cast_seekable_i(); }

This gets called on nullptr when we run (seqable? nil and the obj-> derefs nullptr resulting in a seg fault.

[kiranshila]

Fixed by replacing

inline seekable_i* var::cast<seekable_i>() const { return obj->cast_seekable_i(); }

with

inline seekable_i* var::cast<seekable_i>() const { return obj != nullptr ? obj->cast_seekable_i() : nullptr;}