Avoid a NullPointerException when client roles are associated with a client that no longer exists (#35489)

Closes #34444

Signed-off-by: Giuseppe Graziano <g.graziano94@gmail.com>
(cherry picked from commit 8f417d6318)

Co-authored-by: Marek Posolda <mposolda@gmail.com>

services/src/main/java/org/keycloak/utils/RoleResolveUtil.java

@@ -122,6 +122,9 @@ public class RoleResolveUtil {
 
         } else {
             ClientModel app = (ClientModel) role.getContainer();
+            if (app == null) {
+                return;
+            }
             access = token.getResourceAccess(app.getClientId());
             if (access == null) {
                 access = token.addAccess(app.getClientId());