"Error while updating xray issue types mappings" is returned while trying to update/delete a configuration issue after deleting with success another Issue configuration

Short Description: "Error while updating xray issue types mappings" is returned while trying to update/delete a configuration issue after deleting with success another Issue configuration.

Steps to Reproduce:

1 - Create a Next Gen Project and navigate to Project Settings -> Issue Types option.

2 - Create some Issue Types.

3 - Navigate to Project Settings -> Apps -> NextGen Configuration option, configure some issues and save the configuration.

4 - Update one of the configurations and verify that they are updated with success.

5 - Delete one of the issues by pressing the Back space key and save the configurations.

6 - Try to delete or update other issues and save the configurations.

Actual Result: An error is returned and is not possible to update/delete issues.

Expected Result: The issues should be updated/deleted.