[web2py] error with uploadfield and blob

[richard.ree]

I want to upload a file and store it in a blob field:

db.define_table(
    "data",
    Field("citation", "string", required=True, notnull=True),
    Field("datafile", "upload", uploadfield="data"),
    Field("data", "blob"),
    )

But if I insert a record (through SQLFORM or admin) but leave the
datafile field empty, i.e., I input a citation but not a file, I get
this error:

web2py Version 1.88.2 (2010-10-29 23:04:43)

Traceback (most recent call last):
  File "/home/rree/web2py/gluon/restricted.py", line 188, in
restricted
    exec ccode in environment
  File "/home/rree/web2py/applications/mytest/controllers/
appadmin.py", line 410, in <module>
  File "/home/rree/web2py/gluon/globals.py", line 96, in <lambda>
    self._caller = lambda f: f()
  File "/home/rree/web2py/applications/mytest/controllers/
appadmin.py", line 125, in insert
    if form.accepts(request.vars, session):
  File "/home/rree/web2py/gluon/sqlhtml.py", line 1105, in accepts
    value = fields[fieldname]
KeyError: 'data'

How to make the upload field optional?

Thanks
-Rick