ACS - Unable to retrieve comments for node using REST api after user deletion

Description

• REST api (/nodes/{nodeID}/comments) fails to retrieve comments of node if one of the comments is from a user that has been deleted in the system

Supporting evidence

Steps to reproduce

• Create a new user, in my case the name will be "user1"
• Login as the newly created user and make a comment in one node [see userComment.png]
• The following REST api request (<ALFRESCO_URL>/api/default/public/alfresco/versions/1/nodes/{nodeID}/comments) returns the comment as expected
• Now login as the admin user and delete the newly created user [see userDeleted.png]
• Re-run the REST api request, it will fail

Expected Behaviour

• The REST api request works as expected and the comments for the node are returned

Observed Behaviour

• The REST api request does not work as expected and returns an HTTP 404 error code. The JSON body returned by the request is the following:

  {
      "error": {
          "errorKey": "framework.exception.EntityNotFound",
          "statusCode": 404,
          "briefSummary": "01030003 The entity with id: user1 was not found",
          "stackTrace": "For security reasons the stack trace is no longer displayed, but the property is kept for previous versions",
          "descriptionURL": "https://api-explorer.alfresco.com"
      }
  }