fix issue when adding attributes with non-restricted values

app.py

@@ -112,7 +112,7 @@ def add_attribute_schema(attributes, attr_name, attr_desc, attr_type, allowed_va
     "description": "{attr_desc}",
     "data_type": "{attr_type}",
     "allowed_values": [
-        {', '.join([f'"{v.strip()}"' for v in allowed_values.split(',')])}
+        {', '.join([f'"{v.strip()}"' for v in allowed_values.split(',')]) if allowed_values != "" else ""}
     ]
 }},
 """