Cause:

This issue might be caused by the last entity that the user visited the studio has been deleted, so when the studio is visited again, it will query the last entity that was deleted and the issue occurs.

Solution:

Reset users Studio default display, follow the steps,

1) Have the user login to Agent interface and navigate to the People grid and locate their Person record and note the entity Id (e.g. 17205 )

2) In the URL add &showSampleApp=true and press enter to active the internal REST client.

3) Mega menu->Sample Applications->Utilities

4) In the URL input box enter   personalization/<EntityIdFromStep1>/user  e.g.   personalization/17205/user

5) Change the method to PUT

6) In the input area add

{

    "userId": "17205",

    "personalization": [{

        "key": "last_entity_mgmt_link",

        "value": "{\"state\":{\"url\":\"/entity-generic-tab\",\"templateUrl\":null,\"controller\":null,\"cshid\":\"saEntityGeneric\",\"name\":\"admin_entity-editor_type.entity-generic-tab\"},\"params\":{\"type\":\"Category\"}}"

    }]

}

Where userid is the value from step1 and the same value in the URL in step 4.