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.
if (this.pdfDocument && this.downloadComplete) {
      return;
    }
    throw new Error("PDF document not downloaded.");
  },
  async download({ sourceEventType = "download" } = {}) {
    const url = this.baseUrl,
      filename = this._docFilename;
    try {
      this._ensureDownloadComplete();
      const data = await this.pdfDocument.getData();
      const blob = new Blob([data], { type: "application/pdf" });
      await this.downloadManager.download(blob, url, filename, sourceEventType);
    } catch (reason) {
      
      
      await this.downloadManager.downloadUrl(url, filename);
    }
  },
  async save({ sourceEventType = "download" } = {}) {