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.
PDFViewerApplication.page = PDFViewerApplication.pagesCount;
          handled = true;
          ensureViewerFocused = true;
        }
        break;
    }
  }
  if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC || CHROME")) {
    
    if (cmd === 1 || cmd === 8) {
      switch (evt.keyCode) {
        case 83: 
          eventBus.dispatch("download", { source: window });
          handled = true;
          break;
        case 79: 
          if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
            eventBus.dispatch("openfile", { source: window });
            handled = true;
          }
          break;
      }
    }
  }
  
  if (cmd === 3 || cmd === 10) {
    switch (evt.keyCode) {
      case 80: 
        PDFViewerApplication.requestPresentationMode();
        handled = true;