[web2py] Problem when trying to upload a file in web2py 1.90.4

[Charis]

I have the following error message when i try to upload a file in
web2py 1.90.4. This feature was working fine for me with the previews
versions.

Traceback (most recent call last):
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/gluon/restricted.py",
line 188, in restricted
    exec ccode in environment
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/applications/init/
controllers/default.py", line 150, in <module>
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/gluon/globals.py",
line 95, in <lambda>
    self._caller = lambda f: f()
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/applications/init/
controllers/default.py", line 15, in index
    if form.accepts(request.vars, session):
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/gluon/sqlhtml.py",
line 1104, in accepts
    newfilename = field.store(source_file, original_filename)
  File "/home/charis/Desktop/Dropbox/BioSP_v0.6/gluon/dal.py", line
4132, in store
    path = os.path.join(self.db._adapter.folder, '..', 'uploads')
  File "/usr/lib/python2.6/posixpath.py", line 67, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'NoneType' object has no attribute 'endswith'