TypeError: Cannot read property 'children' of null

[crstffr]

Using a basic implementation of Sortable, I get the following errors thrown continuously as I drag my element around the page. Although it throws nonstop errors, the drag/drop/sort does function correctly.

Environment

• OSX 10.12.6
• Chrome Version 61.0.3163.100 (Official Build) (64-bit)

Error

sortable.js:117 Uncaught TypeError: Cannot read property 'children' of null
    at c (sortable.js:117)
    at a.value (sortable.js:83)
    at a.value (draggable.js:173)
    at a.value (draggable.js:273)
    at a.value (draggable.js:370)
    at g.value (sensor.js:19)
    at g.value (mouse-sensor.js:85)
c @ sortable.js:117
value @ sortable.js:83
value @ draggable.js:173
value @ draggable.js:273
value @ draggable.js:370
value @ sensor.js:19
value @ mouse-sensor.js:85

Simplified Markup

<draggable-container>
  <div ng-if="$ctrl.ready">

    <device-group>
      <button class="drag-handle">
        <i class="fa fa-bars"></i>
      </button>
      <!-- contents item 1-->
    </device-group>  

    <device-group>
      <button class="drag-handle">
        <i class="fa fa-bars"></i>
      </button>
      <!-- contents item N -->
    </device-group> 

  </div>
</draggable-container>

Javascript

let $container = $('draggable-container');
let inst = new Sortable($container, {
  draggable: 'device-group',
  handle: '.drag-handle',
  delay: 200
});

[crstffr]

Some investigation has found that the errors are not thrown when I do not specify my own handle.

Draggable.js:306

const overContainer = sensorEvent.overContainer || this.closestContainer(sensorEvent.target);

Specifying my own handle results in closestContainer() returning null.

Will continue looking...

[crstffr]

It appears like the closestContainer calculations are being done upon the mirror element, which is appended to the body. Therefore the original container is not a parent of the element and the outerContainer value is null.

[crstffr]

In absence of providing an actual fix, I'm just wrapping the offending code in a try/catch. 😐

[tsov]

Re-open or comment if the issue persists with the newest release