witi when input_corpus is NULL

[chainsawriot]

What should be the acceptable behavior of witi(abstracts_stm) or create_oolong(abstracts_stm, type = "witi")?

For old users, it should give you an oolong object with only wi because input_corpus is NULL. It is also the current behavior.

But it can be quite confusing if one asks for wi and ti but only be given an object with wi.