Code is executed in IF statement when condition is not met

I have a sheet with over 400 calendar events and I am trying to write a script that will take these events from my spreadsheet and create events for them in my Google Calendar. To prevent the script from duplicating events every time it runs, I am setting the eventID as a check in the last column of my spreadsheet. The logic is that if the startTime column and endTime columns are not blank and the EventID column IS blank, then the script should run and create a new event, then log the ID into the last column.

I am finding that the code logs an eventID in the last column all the time, which means it creates an event every time, even when the conditions are not met.

function createCalendarEvent() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheetByName('MasterList');
  var data = sheet.getSheetValues(3, 1, sheet.getLastRow(), 12);
  var calendar = CalendarApp.getCalendarById('*CalendarID*');

  for (var i = 0; i <= sheet.getLastRow(); i++) {
    var title = data[i][0]; //String
    var date = new Date(data[i][1]); //Date
    var startTime = new Date(data[i][9]); //DateTime
    var endTime = new Date(data[i][10]); //DateTime
    var location = data[i][5]; //String
    var status = data[i][11]; //String
    var allDay = data[i][3]; //String

    if (allDay === 'ALL DAY' && status === ''){
      var allDayEvent = calendar.createAllDayEvent(title, date, {location: location});
      sheet.getRange(i + 3, 12).setValue(allDayEvent.getId());
    }
    else if (startTime !== '' && endTime !== '' && status === '' ) {
      var event = calendar.createEvent(title, startTime, endTime, {location: location});
      sheet.getRange(i + 3, 12).setValue(event.getId());
    } 
    else {
      Logger.log('\nRow %s is missing start and/or end time or the event has already been created.\n', i + 3);
    }
  }
}