OO-3469: better check variable in velocity template, check if the candidate...

OO-3469: better check variable in velocity template, check if the candidate session exists in disposing phase

src/main/java/org/olat/course/nodes/iq/_content/assessment_run.html

@@ -141,7 +141,7 @@
 	$r.render("highScore")
 #end
 
-#if($showResultsOnHomePage && $attempts > 0)	
+#if($showResultsOnHomePage && $r.isNotNull($attempts) && $attempts > 0)	
 	<div class="panel panel-default o_results">
 	  	<div class="panel-heading">
 	  		<h4 class="panel-title">#if ($showResults && $r.available("command.hideResults"))

src/main/java/org/olat/ims/qti21/ui/AssessmentTestDisplayController.java

@@ -398,9 +398,11 @@ public class AssessmentTestDisplayController extends BasicController implements
 	@Override
 	protected void doDispose() {
 		suspendAssessmentTest(new Date());
-        OLATResourceable sessionOres = OresHelper
-        		.createOLATResourceableInstance(AssessmentTestSession.class, candidateSession.getKey());
-		CoordinatorManager.getInstance().getCoordinator().getEventBus().deregisterFor(this, sessionOres);
+		if(candidateSession != null) {
+			OLATResourceable sessionOres = OresHelper
+					.createOLATResourceableInstance(AssessmentTestSession.class, candidateSession.getKey());
+			CoordinatorManager.getInstance().getCoordinator().getEventBus().deregisterFor(this, sessionOres);
+		}
 	}
 	
 	/**