Updated StubDatabaseDao.

src/test/java/de/thm/arsnova/dao/StubDatabaseDao.java

@@ -425,4 +425,10 @@ public class StubDatabaseDao implements IDatabaseDao {
 		// TODO Auto-generated method stub
 		return null;
 	}
+
+	@Override
+	public List<String> getInactiveUsers(int timeDifference) {
+		// TODO Auto-generated method stub
+		return null;
+	}
 }