KeyError: 'count' on prize acceptance form

[uraniumanchor]

Describe the bug
Seeing this in the error reports. This line in particular, the count key is not present:

        else:
            if self.cleaned_data['count'] == 0:
                raise forms.ValidationError(
                    'You chose accept with 0 prizes. Perhaps you meant to click the other button? If you do not want any of your prizes, simply click the deny button.'
                )

To Reproduce
Steps to reproduce the behavior:

1. Not sure yet. Can't tell from the automated reports if this is the form itself being broken, or not dealing with broken requests robustly.

Expected behavior

Form should display an error if there's an actual error, rather than triggering a 500.