Generated CreateForm: Catch statement throws an error itself (Handle graphql errors properly)

### Problem:

onSubmit handler has a `catch` block:

`
} catch (err) {
          if (onError) {
            const messages = err.errors.map((e) => e.message).join("\n");
            onError(modelFields, messages);
          }
        }
`

err does not necessarily have an `errors` attribute, which will result in an error thrown: `TypeError: Cannot read properties of undefined (reading 'map')`.



