title: Angular app builds white screen after upgrading to version 12
body: <h2>Issue description</h2>
  <p>I recently upgraded Angular app from <code>v11</code> to <code>v12</code>. The whole upgrading process finished successfully without errors. However, when I build my application, application bootstraps as &quot;white screen&quot;, and there are NO errors in the console.</p>
  <p>The result is empty <code>&lt;router-outlet&gt;</code> tag:</p>
  <p><a href="https://i.stack.imgur.com/R2nxO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/R2nxO.png" alt="enter image description here" /></a></p>
  <h2>During debugging I noticed a few things</h2>
  <ol>
  <li>All code from <code>app.component.ts</code> got executed</li>
  <li>Code from <code>main.ts</code> got executed up until the point where app should be bootstrapped:</li>
  </ol>
  <pre class="lang-js prettyprint-override"><code> platformBrowserDynamic().bootstrapModule(AppModule).catch((error) =&gt; {
  </code></pre>
  <ol start="3">
  <li>App only builds &quot;white screen&quot; with <code>ng serve</code> (development build), but builds fine on <code>ng build</code> (production build)</li>
  </ol>
  <h2>Reason of the issue</h2>
  <p>After 2 days of debugging I noticed that when I remove <code>&quot;sourceMap&quot;: true</code> config from <code>angular.json</code> file, application builds fine with <code>ng serve</code> (development build) as well.</p>
  <h2>Question</h2>
  <p>Does anyone know why application builds &quot;white screen&quot; with <code>&quot;sourceMap&quot;: true</code> config and how to prevent it? I would like to keep that config because of debugging purposes.</p>