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.
PDFViewerApplication.pdfViewer.presentationModeState = evt.state;
}
function webViewerSidebarViewChanged(evt) {
  PDFViewerApplication.pdfRenderingQueue.isThumbnailViewEnabled =
    PDFViewerApplication.pdfSidebar.isThumbnailViewVisible;
  const store = PDFViewerApplication.store;
  if (store && PDFViewerApplication.isInitialViewSet) {
    
    store.set("sidebarView", evt.view).catch(function () {});
  }
}
function webViewerUpdateViewarea(evt) {