Fixed 500 on oauthorize page

Author: DheerendraRathor

application/views.py

@@ -37,8 +37,9 @@ def form_valid(self, form):
         scopes = set(scopes.split(' '))
         scopes.update(set(get_default_scopes(application)))
         private_scopes = application.private_scopes
-        private_scopes = set(private_scopes.split(' '))
-        scopes.update(private_scopes)
+        if private_scopes:
+            private_scopes = set(private_scopes.split(' '))
+            scopes.update(private_scopes)
         scopes = ' '.join(list(scopes))
         form.cleaned_data['scope'] = scopes
         return super(CustomAuthorizationView, self).form_valid(form)