Since #12241 we have notifications for this when the user navigates away from the viewer, but we do not yet warn when switching documents, which means that if you call e.g. `PDFViewerApplication.open` with a new document (or directly call `BaseViewer.setDocument` when using the viewer components standalone) there won't be any warning about losing form data. This should be addressed.
if (!this.documentInfo) {
      
      
      await new Promise(resolve => {
        this.eventBus._on("metadataloaded", resolve, { once: true });
      });
      if (pdfDocument !== this.pdfDocument) {
        return null; 
      }
    }
    if (!this._contentLength) {
      
      
      
      
      
      await new Promise(resolve => {
        this.eventBus._on("documentloaded", resolve, { once: true });
      });
      if (pdfDocument !== this.pdfDocument) {
        return null; 
      }
    }
    return {