title: what does formControl.value?.length do?
body: <p>I understand its not the best post. But I saw this line of code in the material multi select custom trigger example.</p>
  
  <p><code>*ngIf="toppings.value?.length &gt; 1"</code>
   <a href="https://stackblitz.com/angular/omvmgjjbnnq?file=app%2Fselect-custom-trigger-example.html" rel="nofollow noreferrer">https://stackblitz.com/angular/omvmgjjbnnq?file=app%2Fselect-custom-trigger-example.html</a></p>
  
  <p>I don't understand what the "?" is doing here and I am having a hard time even googling what it could be (google doesn't like question marks). Does this allow you to call a property of <code>value</code> safely without having to check if <code>value</code> is defined or null?</p>