PDF.js version: 3.5.141

These two properties should be marked as not mandatory as they are initialized if not present
let spread = null;
        for (let i = 0, ii = pages.length; i < ii; ++i) {
          if (spread === null) {
            spread = document.createElement("div");
            spread.className = "spread";
            viewer.append(spread);
          } else if (i % 2 === parity) {
            spread = spread.cloneNode(false);
            viewer.append(spread);
          }
          spread.append(pages[i].div);
        }
      }
    }
    if (!pageNumber) {
      return;
    }
    
    
    
    if (this._currentScaleValue && isNaN(this._currentScaleValue)) {
      this.#setScale(this._currentScaleValue, { noScroll: true });
    }
    this._setCurrentPageNumber(pageNumber,  true);
    this.update();
  }
  /**
   * @private
   */
  _getPageAdvance(currentPageNumber, previous = false) {