Revert "[FIX] website: redirect only when url_to given"

This reverts commit 14a8509.

addons/website/models/website_rewrite.py

@@ -82,7 +82,7 @@ def _onchange_route_id(self):
     @api.constrains('url_to', 'url_from', 'redirect_type')
     def _check_url_to(self):
         for rewrite in self:
-            if rewrite.redirect_type in ['301', '302', '308']:
+            if rewrite.redirect_type == '308':
                 if not rewrite.url_to:
                     raise ValidationError(_('"URL to" can not be empty.'))
                 if not rewrite.url_from: