fixed pydanticv1 issue

Author: Andrei Neagu

packages/models-library/src/models_library/api_schemas_catalog/services.py

@@ -205,7 +205,10 @@ class ServiceUpdate(ServiceMetaDataEditable, ServiceAccessRights):
 class ServiceGet(
     ServiceMetaDataPublished, ServiceAccessRights, ServiceMetaDataEditable
 ):  # pylint: disable=too-many-ancestors
-    owner: LowerCaseEmailStr | None
+    owner: LowerCaseEmailStr | None = Field(
+        None,
+        description="None when the owner email cannot be found in the database",
+    )
 
     model_config = ConfigDict(
         extra="ignore",