Fix StopIteration error thrown in view collections page
Fix StopIteration error thrown in view collections page

* wqflask/wqflask/user_session.py (user_id): Use byte-string when
fetching user_id. See:
https://github.com/genenetwork/genenetwork2/pull/422#issuecomment-701082458

pjotrp/genenetwork2,genenetwork/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,pjotrp/genenetwork2,genenetwork/genenetwork2,zsloan/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2