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.
errorWrapper.hidden = false;
      const errorMessage = errorWrapperConfig.errorMessage;
      errorMessage.textContent = message;
      const closeButton = errorWrapperConfig.closeButton;
      closeButton.onclick = function () {
        errorWrapper.hidden = true;
      };
      const errorMoreInfo = errorWrapperConfig.errorMoreInfo;
      const moreInfoButton = errorWrapperConfig.moreInfoButton;
      const lessInfoButton = errorWrapperConfig.lessInfoButton;
      moreInfoButton.onclick = function () {
        errorMoreInfo.hidden = false;
        moreInfoButton.hidden = true;
        lessInfoButton.hidden = false;
        errorMoreInfo.style.height = errorMoreInfo.scrollHeight + "px";
      };
      lessInfoButton.onclick = function () {
        errorMoreInfo.hidden = true;
        moreInfoButton.hidden = false;
        lessInfoButton.hidden = true;
      };
      moreInfoButton.oncontextmenu = noContextMenuHandler;
      lessInfoButton.oncontextmenu = noContextMenuHandler;
      closeButton.oncontextmenu = noContextMenuHandler;
      moreInfoButton.hidden = false;
      lessInfoButton.hidden = true;
      Promise.all(moreInfoText).then(parts => {
        errorMoreInfo.value = parts.join("\n");
      });
    } else {