SAK-50810 Assignment in peer review attachmentRefList maybe null (#13149)

Author: ern

assignment/tool/src/java/org/sakaiproject/assignment/entityproviders/AssignmentEntityProvider.java

@@ -2247,7 +2247,9 @@ public SimplePeerAssessmentItem(PeerAssessmentItem item) {
             this.scaledFactor = item.getScaledFactor();
             this.draft = item.isDraft();
 
-            this.attachmentUrlList = item.getAttachmentRefList().stream()
+            this.attachmentUrlList = Optional.ofNullable(item.getAttachmentRefList())
+                    .orElseGet(Collections::emptyList)
+                    .stream()
                     .map(Reference::getUrl)
                     .collect(Collectors.toList());
         }