title: Angular Ivy strictTemplates true Type 'boolean | null' is not assignable to type 'boolean'
body: <p>I've updated my app to 9 version.
  Everything is alright but I've problem
  with strictTemplates set to true.
  For instance this code</p>
  
  <pre><code>loaded$: Observable&lt;boolean&gt;
  [loaded]="loaded$ | async"
  @Input() loaded!: boolean;
  </code></pre>
  
  <p>I've got the error Type 'boolean | null' is not assignable to type 'boolean'.</p>
  
  <p>This fix the error</p>
  
  <pre><code>@Input() loaded!: boolean | null;
  </code></pre>
  
  <p>But I cant see the point someone acn explain me, please?</p>