Exception in thread "main" java.time.format.DateTimeParseException: Text '' could not be parsed at index 0;at EventManager.main(EventManager.java:26)

Question

I am trying to get make an event manager. I take start time end time and event name. then store in an a list.it worked fine for single input. however when I applied a do while loop it just gave exception. below is the code. Any help or Suggestion on what I am doing wrong or what I need to do.

   do {
        
    System.out.println("Enter event start time HH:MM");
    String St = sc.nextLine();
    LocalTime st = LocalTime.parse(St); //it gives exception here.
    
    System.out.println("Enter event Ending time HH:MM");
    String Et = sc.nextLine();
    LocalTime et = LocalTime.parse(Et);
    
    System.out.println(st + "-" +et +" " +Ename);
    
    System.out.println("Enter Event Name");
    String Ename = sc.nextLine();
    e1 = new Event(st,et,Ename);


    events.add(e1);
    System.out.println(e1.getStartTime() + "-" +e1.getEndTime() +" " +e1.getEventname());
    System.out.println("Press '1' to enter another event");
    int ch= sc.nextInt();
     if(ch != 1) choice = false;
    }
    while(choice=true);