Index: lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/web/controller/LearningController.java
===================================================================
diff -u -r292df3a6fb3cce2b31c9d9ee33c61bbe931e58ab -rfc1a904cdec5fa044954ace5778c84a9a7db35a8
--- lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/web/controller/LearningController.java	(.../LearningController.java)	(revision 292df3a6fb3cce2b31c9d9ee33c61bbe931e58ab)
+++ lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/web/controller/LearningController.java	(.../LearningController.java)	(revision fc1a904cdec5fa044954ace5778c84a9a7db35a8)
@@ -1173,6 +1173,7 @@
 	// Item IDs are AssessmentQuestionResults UIDs, i.e. a user answer for a particular question
 	// Get all item IDs no matter which session they belong to.
 	Set<Long> itemIds = questionSummaries.values().stream().flatMap(s -> s.getQuestionResultsPerSession().stream())
+		.filter(l -> l != null && !l.isEmpty())
 		.collect(Collectors.mapping(l -> l.get(l.size() - 1).getUid(), Collectors.toSet()));
 
 	List<ItemRatingDTO> itemRatingDtos = ratingService.getRatingCriteriaDtos(assessment.getContentId(), null,