Merge branch 'fix-session-import' into '2.5'

Fix session import

See merge request !49

src/main/java/de/thm/arsnova/entities/transport/ImportExportSession.java

@@ -155,6 +155,10 @@ public class ImportExportSession {
 
 		private List<Answer> answers;
 
+		public ImportExportQuestion() {
+
+		}
+
 		public ImportExportQuestion(Question q) {
 			setType(q.getType());
 			setQuestionType(q.getQuestionType());