STR:
  - Go to https://mozilla.github.io/pdf.js/web/viewer.html
  - Click on "Open File" and open a pdf

The `Download` button and the `Current view` one just disappear.
I can reproduce this bug with Firefox nightly, Chrome stable and Epiphany on debian.
const { appConfig, externalServices } = this;
    let eventBus;
    if (appConfig.eventBus) {
      eventBus = appConfig.eventBus;
    } else if (externalServices.isInAutomation) {
      eventBus = new AutomationEventBus();
    } else {
      eventBus = new EventBus();
    }
    this.eventBus = eventBus;
    this.overlayManager = new OverlayManager();
    const pdfRenderingQueue = new PDFRenderingQueue();
    pdfRenderingQueue.onIdle = this._cleanup.bind(this);
    this.pdfRenderingQueue = pdfRenderingQueue;
    const pdfLinkService = new PDFLinkService({
      eventBus,
      externalLinkTarget: AppOptions.get("externalLinkTarget"),
      externalLinkRel: AppOptions.get("externalLinkRel"),
      ignoreDestinationZoom: AppOptions.get("ignoreDestinationZoom"),
    });
    this.pdfLinkService = pdfLinkService;
    const downloadManager = externalServices.createDownloadManager();
    this.downloadManager = downloadManager;
    const findController = new PDFFindController({
      linkService: pdfLinkService,
      eventBus,