title: Laravel Collective select to output null when submitted
body: <p>I am using Laravel Collective for creating my webform.</p>
  
  <pre><code>{!! Form::select('сity_from', ['London', 'Tokyo', 'Moscow'], null, ['placeholder' =&gt;  'Choose city'] )  !!}
  </code></pre>
  
  <p>which produces the following html:</p>
  
  <pre><code>&lt;select id="сity_from" name="сity_from"&gt;
  &lt;option selected="selected" disabled="disabled" hidden="hidden" value&gt;Choose city&lt;/option&gt;
  &lt;option value="London"&gt;London&lt;/option&gt;
  &lt;option value="Tokyo"&gt;Tokyo&lt;/option&gt;
  &lt;option value="Moscow"&gt;Moscow&lt;/option&gt;
  </code></pre>
  
  <p>when I choose no city and submit form, and then <code>dd($request-&gt;all());</code>in Controller<code>
  </code>i can see nothing, I mean, there is no <code>$request-&gt;all()['city_from']</code>;</p>
  
  <p>I would like to get <code>['city_from' = null]</code> in this case.</p>
  
  <p>I suppose I have to change 'value' in </p>
  
  <pre><code>&lt;option selected="selected" disabled="disabled" hidden="hidden" value&gt;Choose city&lt;/option&gt;
  </code></pre>
  
  <p>to value="null"?</p>
  
  <p>Or something else?</p>
  
  <p>I would like to be using Laravel Collective when solving this problem.</p>