[web2py] GAE - DAL problem

[felixdm]

I have this problem in GAE

Traceback (most recent call last):
  File "/base/data/home/apps/s~book-on/1.353593485285740911/gluon/
restricted.py", line 194, in restricted
    exec ccode in environment
  File "/base/data/home/apps/s~book-on/1.353593485285740911/
applications/bookon/controllers/default.py:user", line 204, in
<module>
  File "/base/data/home/apps/s~book-on/1.353593485285740911/gluon/
globals.py", line 149, in <lambda>
    self._caller = lambda f: f()
  File "/base/data/home/apps/s~book-on/1.353593485285740911/
applications/bookon/controllers/default.py:user", line 149, in user
AttributeError: 'NoneType' object has no attribute 'id'



                if request.args(0)=="register":
                        if not request.args(1) or (request.args(1)!="teacher" 
and
request.args(1)!="student" and request.args(1)!="institution"):
                                redirect(URL(r=request,c='default',f='index'))

        
form=SQLFORM(db.auth_user,fields=['fullname','email','password','username'],formstyle='divs')

                        if form.accepts(request.vars, session, dbio=True):

                                if request.args(1)=="teacher":

                                        tid = 
db.auth_group(description="Teacher").id             <- 149
NoneType DAL problem?
                                        username_id = 
db.auth_user(username=request.vars['username']).id
                                        auth.add_membership( tid , username_id)