Incompatibility with a_b relationships

Since https://github.com/civicrm/civicrm-core/pull/13916, the Case Roles panel will not display correctly if the case had relationships created with a_b relationships.

To reproduce:

Create a blank CiviCRM instance, enable CiviCase
Create a new case, and add a child and a parent to the case (for both directions)

Error: "role in roles"

Capture d’écran de 2019-06-12 11-42-38

Debugging ang/civicase/ViewPeople.js, I see that the $scope.roles has, for example:

Capture d’écran de 2019-06-12 12-01-36

civicrm / org.civicrm.civicase