title: Angular How to make [formControl] an optional field
body: <p>In Angular you can add attributes to inputs and make them optional using attr:</p>
  <pre class="lang-html prettyprint-override"><code>&lt;input [type]=&quot;text&quot; [attr.id]=&quot;id&quot;&gt;
  </code></pre>
  <p>But how do you make a form control optional? I want something like this:</p>
  <pre class="lang-html prettyprint-override"><code>&lt;input [type]=&quot;text&quot; [attr.formControl]=&quot;someControl&quot;&gt;
  </code></pre>
  <p>Where the formControl will not be set if someControl is undefined or null?</p>