The "display" form handler of the "facets_facet_source" entity type specifies a non-existent class "Drupal\facets\Form\FacetSourceDisplayForm"

Problem/Motivation

I discovered this error while getting a list of forms for entities with a custom code

Steps to reproduce

Go to the facets_facet_source entity definition and you will notice the display and delete forms doesn't exists in the module

*       "display" = "Drupal\facets\Form\FacetSourceDisplayForm",
 *       "delete" = "Drupal\facets\Form\FacetSourceDeleteConfirmForm",

Proposed resolution

Add the forms or remove the lines.