bug#34852: 26.1; seq-intersection ignores nil as element

[Basil L. Contovounesios]

"Miguel V. S. Frasson" <mvsfrasson@gmail.com> writes:

> In https://lists.gnu.org/archive/html/emacs-devel/2016-07/msg01256.html
> it is mentioned that:
>
>>    I believe `seq-contains' was introduced for convenience:
>>    it is used elsewhere in seq.el and map.el.
>
> so there may be problems in map.el as well if it is used as a
> predicate there, or even in more files.

All occurences of seq-contains I could find in emacs.git are addressed
in the two patches.

Thanks,

-- 
Basil