[playground] handle when transformOutput is null

[henryqdineen]

Summary

The React Compiler Playground was crashing for me with a error that said "Application error: a client-side exception has occurred while loading playground.react.dev". I could only fix it by clearing the browser data

Console error:

Uncaught TypeError: Cannot read properties of undefined (reading 'code')
    at R (2718.2ef44c120f1f0fb2.js:1:2240553)
    at 2718.2ef44c120f1f0fb2.js:1:2242468
    at V (2718.2ef44c120f1f0fb2.js:1:2242518)

Problematic source code:

import { UIHeader } from 'somewhere';

const Header = ({
  breadcrumbs = <div className="foo" />, 
}) => {
  return (
    <UIHeader breadcrumbs={breadcrumbs}/>      
  );
};

I tracked this down to a bug that I think should be caught by TypeScript since CompilerTransformOutput['transformOutput'] is non-nullable. My fix was to move the return statements into the try and catch blocks. I had something slightly different in an initial fix but I was confused by otherErrors and hasErrors().

How did you test this change?

Tested locally. Screen shot attached.