title: Laravel sync not working with empty array
body: <p>I've a method looks like this:</p>
  
  <pre><code>public function saveContacts(Request $request)
  {
      if($request-&gt;contacts) {
          $contacts = collect($request-&gt;contacts)-&gt;pluck('id');
          $this-&gt;contacts()-&gt;sync($contacts-&gt;toArray());
      }
  }
  </code></pre>
  
  <p>It's working but if <code>$request-&gt;contacts</code> is an empty array it does not remove all records. What could be the case here?</p>