title: Uncaught TypeError: Cannot read property 'top' of null in fullCalendar
body: <p>For fullCalendar I have written the code below: </p>
  
  <pre><code>$('#mycalendar').fullCalendar(
              {
                  allDaySlot:false,
                  slotDuration: '00:30:00' ,  
                  //slotMinutes: '120',           
                  lang: currentLangCode,
                  minTime: '4:00am',
                  maxTime: '24:00pm',
                  slotEventOverlap: true,
                  slotLabelFormat:'h(:mm)a',
                  showAgendaButton: true,
                  columnFormat: { month: 'ddd', week: 'ddd M/D', day: 'ddd M/D' },
                  timeFormat: 'H:mm',
                  defaultView: 'listWeek',
                  eventLimit: true,
                  theme:false,
                  editable: true,
                  contentHeight:'auto',
                  weekends: false ,
                  //timezoneParam: 'America/Los_Angeles',
                  //ignoreTimezone: false,
                  header:
                  {
                      left: 'prev,next today',
                      center: 'title',
                      // right: 'agendaWeek'
                      right: 'month,agendaWeek,agendaDay,listWeek'
                  },
                  views: {
                      listDay: { buttonText: 'Day' },
                      listWeek: { buttonText: 'Week' },
                      month: {
                          columnFormat: 'ddd'
                      },
                      agenda: {
                          columnFormat: 'ddd'
                      }
                  },
  </code></pre>
  
  <p>I am getting below error for agendaWeek and agendaDay:</p>
  
  <p><a href="https://i.stack.imgur.com/DAnmr.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DAnmr.jpg" alt="enter image description here"></a></p>
  
  <p>I am using: </p>
  
  <p>jQuery JavaScript Library v3.3.1
  FullCalendar v3.9.0</p>