sp_fr: ignore empty data when transfering requests to w.c.s. (#32849)

passerelle/apps/sp_fr/models.py

@@ -314,6 +314,8 @@ class Resource(BaseResource):
                         context = data.copy()
                         context['value'] = value
                         value = template.render(context)
+                    if not value:
+                        continue
                     submitter.set(name, value)
             return submitter.result.backoffice_url