Fix unit tests with new license support

Make the license field in the forms optional and let them
properly be defaulted to "".

mediagoblin/submit/forms.py

@@ -39,4 +39,5 @@ class SubmitStartForm(wtforms.Form):
           "Separate tags by commas."))
     license = wtforms.SelectField(
         _('License'),
+        [wtforms.validators.Optional(),],
         choices=licenses_as_choices())

mediagoblin/submit/views.py

@@ -69,9 +69,7 @@ def submit_start(request):
                 entry.description_html = cleaned_markdown_conversion(
                     entry.description)
 
-                entry.license = (
-                    unicode(request.POST.get('license'))
-                    or '')
+                entry.license = unicode(request.POST.get('license', ''))
 
                 entry.uploader = request.user._id