Check if user is anonymous before calling PSYCHOMETRICS

LTI grade callbacks for example, come in with an anonymous user.  This causes a
stack trace in the psychometrics app that leads to the LTI service
getting a 404.  This adds a check before that callback gets registered.

lms/djangoapps/courseware/module_render.py

@@ -512,8 +512,7 @@ def get_module_system_for_user(user, field_data_cache,
             position = None
 
     system.set('position', position)
-
-    if settings.FEATURES.get('ENABLE_PSYCHOMETRICS'):
+    if settings.FEATURES.get('ENABLE_PSYCHOMETRICS') and user.is_authenticated():
         system.set(
             'psychometrics_handler',  # set callback for updating PsychometricsData
             make_psychometrics_data_update_handler(course_id, user, descriptor.location)