Issue description

I recently upgraded Angular app from v11 to v12. The whole upgrading process finished successfully without errors. However, when I build my application, application bootstraps as "white screen", and there are NO errors in the console.

The result is empty <router-outlet> tag:

During debugging I noticed a few things

1. All code from app.component.ts got executed
2. Code from main.ts got executed up until the point where app should be bootstrapped:

 platformBrowserDynamic().bootstrapModule(AppModule).catch((error) => {

3. App only builds "white screen" with ng serve (development build), but builds fine on ng build (production build)

Reason of the issue

After 2 days of debugging I noticed that when I remove "sourceMap": true config from angular.json file, application builds fine with ng serve (development build) as well.

Question

Does anyone know why application builds "white screen" with "sourceMap": true config and how to prevent it? I would like to keep that config because of debugging purposes.