Cast to ObjectId failed for value \"\" at path

Hello every one,

Is there anyway that we can handle this type of error (MongoDB and GraphQL)
I sending blank value for a field that is relation field type - on our current setup, that particular field is optional, but strapi/graphql keeps throwing me this error.

> Cast to ObjectId failed for value “” at path

Hope you can help

Is this on the user model?

I have the same issue.
This is not only on the user model, but on all relations in the strapi model (also the custom models)