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.
this._contentLength ??= contentLength; 
    
    console.log(
      `PDF ${pdfDocument.fingerprints[0]} [${info.PDFFormatVersion} ` +
        `${(info.Producer || "-").trim()} / ${(info.Creator || "-").trim()}] ` +
        `(PDF.js: ${version || "-"})`
    );
    let pdfTitle = info?.Title;
    const metadataTitle = metadata?.get("dc:title");
    if (metadataTitle) {
      
      
      
      
      
      
      if (
        metadataTitle !== "Untitled" &&
        !/[\uFFF0-\uFFFF]/g.test(metadataTitle)
      ) {
        pdfTitle = metadataTitle;
      }
    }
    if (pdfTitle) {
      this.setTitle(
        `${pdfTitle} - ${contentDispositionFilename || document.title}`
      );
    } else if (contentDispositionFilename) {
      this.setTitle(contentDispositionFilename);
    }