I found the description very clear (at least in Python where I did it)
with a line full of spaces, remove them, you end up with ''
with an empty line, keep it as empty line ''
if you have many, like
aaaaa

bbbbb

keep that empty line in the middle, since according to the tests, '\n' gives '\n' (you can have a look at the tests below as examples)

Strongly agree. Description is not clear on all cases.

You've passed the kata, that's for the first part. About the second part, duplicated issue. Closing.

My java solution is recursive and it works.