powermail

When exporting a form containing non-mandatory radio buttons, the export (csv or excel) contains a very annoying bug.

Reproduce:
- Create a form containing several fields, but at least one non-mandatory radio button field
- Fill in the form NOT SELECTING any of the radio buttons; send it
- Fill in the form selecting one of the radio buttons; send it
- Export
- Look at the csv or Excel file

You'll see that the export doesn't contain the specific radio button field for the entry where you didn't click anything. At all. And so, all other columns are moved to the left, which makes it impossible to use the data exported in a useful way. We have used Powermail for the subscriptions to an event, and it's very annoying to see that exporting over 300 subscriptions still doesn't give you an useful list of names and email addresses.
I'd say this should be fixed by explicitly adding ALL fields to the database after sending a form, and not just the filled in ones. I can't exactly find in which file this should be fixed, so I can't give an example bug fix right now. But I think it's an important bug to keep the export function a useful feature.