This error is because there is a property field in that model, on that form that doesn't have his generic value defined, probably someone delete it.
you should be getting this same error one time for every property with no generic value inside that form.
the model is the object, for example the partner 'res.partner'
What is a property field?
Where can I define the generic value?
first you need to know the property you are going define, to know that, get developer mode on that form and check for fields that begins with 'property', properties are usually accounts, in res.partner we also have the price-lists.
so lets say for example our property is 'property_account_receivable' from the partner object, which is a many2one field to the object account.account
now we go to settings --> parameters --> configuration parameters
we filter for generics and search for it, if there is no lines, then thats a problem and we need one.
so we create one with the name:'property_account_receivable', field: Account Receivable, type:many2one, resource:[no value], account.account, and the default account we would want to put.