Use the default release if it isn't in the form.

This happens with manual querystring hacking sometimes.

django_website/docs/forms.py

@@ -18,7 +18,7 @@ def __init__(self, *args, **kwargs):
 
     def search(self):
         sqs = super(DocSearchForm, self).search()
-        rel = self.cleaned_data['release']
+        rel = self.cleaned_data.get('release', DocumentRelease.objects.default())
         return sqs.filter(lang=rel.lang, version=rel.version)
 
 class DocumentReleaseChoiceField(forms.ModelChoiceField):