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 (pdfDocument !== this.pdfDocument) {
      return;
    }
    const { annotationStorage } = pdfDocument;
    annotationStorage.onSetModified = () => {
      window.addEventListener("beforeunload", beforeUnload);
      if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
        this._annotationStorageModified = true;
      }
    };
    annotationStorage.onResetModified = () => {
      window.removeEventListener("beforeunload", beforeUnload);
      if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
        delete this._annotationStorageModified;
      }
    };
  },
  setInitialView(