[web2py] Re: default values in options widget

[Oleg]

As far as I understood, the problem is that, it is not possible (??) in 
current web2py crud implementation to map one label in dropdown control to 
database NULL value.
If you do IS_IN_SET({None:'Unknown','Opt1':'Opt1', 'Opt2':'Opt2'}, 
zero=None) and submit the 'Unknown', you become 'None' as string in DB, but 
not NULL.. and in other direction there is the same problem. NULL value in 
DB will not initialize 'Unknown' value in dropdown control