erp5_hal_json_style: fix bug when empty portal type list is returned

bt5/erp5_hal_json_style/SkinTemplateItem/portal_skins/erp5_hal_json_style/ERP5Document_getHateoas.xml

@@ -133,14 +133,20 @@ def renderField(field, meta_type=None):\n
       "required": field.get_value("required"),\n
     }\n
   elif meta_type in ("RelationStringField", "MultiRelationStringField"):\n
+    \n
+    portal_type_list = field.get_value(\'portal_type\');\n
+    if len(portal_type_list) > 0:\n
+      portal_types = portal_type_list[0]\n
+    else:\n
+      portal_types = []\n
+    \n
     query = url_template_dict["jio_search_template"] % {\n
       "query": make_query({"query": sql_catalog.buildQuery(\n
-        {"portal_type": [x[0] for x in field.get_value(\'portal_type\')]}\n
+        {"portal_type": [x[0] for x in portal_types]}\n
       ).asSearchTextExpression(sql_catalog)})\n
     }\n
     result = {\n
-      "portal_types": field.get_value(\'portal_type\')[0],\n
-      #"query": url_template_dict["jio_search_template"],\n
+      "portal_types": portal_types,\n
       "query": query,\n
       "catalog_index": field.get_value(\'catalog_index\'),\n
       "allow_jump": field.get_value(\'allow_jump\'),\n