js синтаксис... Ошибка генерируется

// Структура:
class OHLCTime {
  constructor() {
    this.Open = null;
    this.High = null;
    this.Low = null;
    this.Close = null;
    this.Time = null;
  }
}



// Фрагмент проблемного кода:
let first = [];
let firstIndex = 0;
let second = [];
let secondIndex = 0;
let count = 0;
let temp = "";
for (let i = 0; i < firstHistory.length; ++i) {
  if (firstHistory[i] != ";") {
    temp += firstHistory[i];
  }
  else {
    if (count == 0) {
      count++;
      first[firstIndex] = new OHLCTime();
      first[firstIndex].Open = temp;
      temp = "";
    }
    else if (count == 1) {
      count++;
      first[firstIndex].High = temp;
      temp = "";
    }
    else if (count == 2) {
      count++;
      first[firstIndex].Low = temp;
      temp = "";
    }
    else if (count == 3) {
      count++;
      first[firstIndex].Close = temp;
      temp = "";
    }
    else { // == 4
      count == 0;
      first[firstIndex++].Time = temp;  // Здесь сервер указывает на ошибку в этой строке.
      temp = "";
    }
  }
}
count = 0;

Текст ошибки: TypeError: Cannot set property 'Time' of undefined
at /var/www/www-root/data/www/invizzz.com/nodejs/listenMQL.js:498:80
at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:63:3)