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.
const cssTheme = AppOptions.get("viewerCssTheme");
    if (
      cssTheme === ViewerCssTheme.AUTOMATIC ||
      !Object.values(ViewerCssTheme).includes(cssTheme)
    ) {
      return;
    }
    try {
      const styleSheet = document.styleSheets[0];
      const cssRules = styleSheet?.cssRules || [];
      for (let i = 0, ii = cssRules.length; i < ii; i++) {
        const rule = cssRules[i];
        if (
          rule instanceof CSSMediaRule &&
          rule.media?.[0] === "(prefers-color-scheme: dark)"
        ) {
          if (cssTheme === ViewerCssTheme.LIGHT) {
            styleSheet.deleteRule(i);
            return;
          }
          
          const darkRules =
            /^@media \(prefers-color-scheme: dark\) {\n\s*([\w\s-.,:;/\\{}()]+)\n}$/.exec(
              rule.cssText
            );
          if (darkRules?.[1]) {
            styleSheet.deleteRule(i);
            styleSheet.insertRule(darkRules[1], i);
          }