title: Cancel dragging of a sortable item
body: <p>An absolutely common sortable case:</p>
  
  <pre><code>&lt;script&gt;
  $(function() {
    $("#sortable").sortable();
  });
  &lt;/script&gt;
  
  &lt;ul id="sortable"&gt;
    &lt;li&gt;Item 1&lt;/li&gt;
    &lt;li&gt;Item 2&lt;/li&gt;
    &lt;li&gt;Item 3&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p><strong>Problem.</strong> Need to cancel dragging of an item on some condition and there is a good advice of  <a href="https://stackoverflow.com/questions/5006271/jquery-draggablecancel-causing-error-this-helper-is-null/5012029#5012029">Andrew Whitaker</a>, but that approach is working only for jquery-ui-draggable and fails for sortables:</p>
  
  <pre><code>$("#sortable").sortable({
    start: function() {
      return false; // will still cause `this.helper is null`
    }
  });
  </code></pre>
  
  <p>Will be greateful for suggestions.</p>