OO-2670: add security if an assignment of the list doesn't exists

src/main/java/org/olat/modules/portfolio/manager/BinderDAO.java

@@ -36,6 +36,8 @@ import org.olat.basesecurity.Invitation;
 import org.olat.basesecurity.manager.GroupDAO;
 import org.olat.core.commons.persistence.DB;
 import org.olat.core.id.Identity;
+import org.olat.core.logging.OLog;
+import org.olat.core.logging.Tracing;
 import org.olat.core.util.StringHelper;
 import org.olat.modules.portfolio.Assignment;
 import org.olat.modules.portfolio.AssignmentStatus;
@@ -67,6 +69,8 @@ import org.springframework.stereotype.Service;
  */
 @Service
 public class BinderDAO {
+	
+	private static final OLog log = Tracing.createLoggerFor(BinderDAO.class);
 
 	@Autowired
 	private DB dbInstance;
@@ -248,6 +252,11 @@ public class BinderDAO {
 		
 		List<Assignment> currentAssignments = new ArrayList<>(currentSection.getAssignments());
 		for(Assignment currentAssignment:currentAssignments) {
+			if(currentAssignment == null) {
+				log.error("Missing assignment: " + currentSection.getKey());
+				continue;
+			}
+			
 			Assignment refAssignment = currentAssignment.getTemplateReference();
 			if(refAssignment == null) {
 				if(currentAssignment.getAssignmentStatus() != AssignmentStatus.deleted) {