Update twitter/follow.py

Sometimes Twitter returns a list of any user without ID.
Users blocked or suspended? I do not know.
This modification prevents the script to stop and return an incomplete list.
Merge pull request #118 from DracoThuban/patch-1

Update twitter/follow.py
Sometimes Twitter returns a list of any userID without user.
Users blocked or suspended? I don't know.
This modification prevents the script to stop and return an incomplete list.