When using viewer.js code in an iframe (`web/viewer.html?file=my.pdf"`) and getting a load error like `Error: file origin does not match viewer's` how do I catch this error?  The console reports `app.js:2140 Uncaught (in promise) Error: file origin does not match viewer's`.  I have setup the load listener and am using the `PDFViewerApplication.initializedPromise`.  I was hoping the `PDFViewerApplication.initializedPromise` would reject, but it does not.  I could not find an eventbus event to listen to specifically for load errors either.

I would like to programmatically detect such load errors and dynamically remove the iframe hosting the pdf viewer and instead replace it with my own error messaging.  I can't figure out how to do that.

Configuration:
- Any, but testing on Chrome 97.0.4692.71 64-bit
- Ubuntu 20.04
- PDF.js version:  v2.12.313
- Is a browser extension: No

Steps to reproduce the problem:
1.  Purposely try to load a PDF in a way that would cause the `app.js:2140 Uncaught (in promise) Error: file origin does not match viewer's` error.
};
    
    loadingTask.onUnsupportedFeature = this.fallback.bind(this);
    return loadingTask.promise.then(
      pdfDocument => {
        this.load(pdfDocument);
      },
      reason => {
        if (loadingTask !== this.pdfLoadingTask) {
          return undefined; 
        }
        let key = "loading_error";
        if (reason instanceof InvalidPDFException) {
          key = "invalid_file_error";
        } else if (reason instanceof MissingPDFException) {
          key = "missing_file_error";
        } else if (reason instanceof UnexpectedResponseException) {
          key = "unexpected_response_error";
        }
        return this.l10n.get(key).then(msg => {
          this._documentError(msg, { message: reason?.message });
          throw reason;
        });
      }
    );
  },
  /**
   * @private
   */
  _ensureDownloadComplete() {