Error while resizing with golden layout: Cannot read property 'appendChild' of null

/**
     * Initialize module. Automatically called with a new instance of the editor
     * @param {Object} config Configurations
     * @return {this}
     * @private
     */
`
    init(conf = {}) {
      c = {
        ...defaults,
        ...conf
      };
      const em = c.em;
      const ppfx = c.pStylePrefix;
      this.em = em;

      if (ppfx) {
        c.stylePrefix = ppfx + c.stylePrefix;
      }

      this.selectorTags = new ClassTagsView({
        collection: new Selectors([], { em, config: c }),
        config: c
      });

      // Global selectors container
      selectors = new Selectors(c.selectors);
      selectors.on('add', model => em.trigger('selector:add', model));
      selectors.on('remove', model => em.trigger('selector:remove', model));
      selectors.on('change', model =>
        em.trigger(
          'selector:update',
          model,
          model.previousAttributes(),
          model.changedAttributes()
        )
      );
      em.on('change:state', (m, value) => em.trigger('selector:state', value));

      return this;
    },

    postRender() {
      const elTo = this.getConfig().appendTo;

      if (elTo) {
        const el = isElement(elTo) ? elTo : document.querySelector(elTo);
        el.appendChild(this.render([])); //this line error
      }
    },

    select(value, opts = {}) {
      const targets = Array.isArray(value) ? value : [value];
      const toSelect = this.em.get('StyleManager').setTarget(targets, opts);
      const res = toSelect
        .filter(i => i)
        .map(sel =>
          isComponent(sel)
            ? sel
            : isRule(sel) && !sel.get('selectorsAdd')
            ? sel
            : sel.getSelectorsString()
        );
      this.selectorTags.componentChanged({ targets: res });
      return this;
    },`


![image](https://user-images.githubusercontent.com/6602723/73726047-a2ff4d00-4769-11ea-887c-9e3d2d71ed51.png)


`index.js:129 Uncaught TypeError: Cannot read property 'appendChild' of null
    at Object.postRender (index.js:129)
    at index.js:757
    at Array.forEach (<anonymous>)
    at r.<anonymous> (index.js:756)
    at m (backbone.js:368)
    at v (backbone.js:356)
    at h (backbone.js:155)
    at r.c.trigger (backbone.js:346)
    at renderBody (CanvasView.js:263)
    at I (underscore.js:762)
postRender @ index.js:129
(anonymous) @ index.js:757
(anonymous) @ index.js:756
m @ backbone.js:368
v @ backbone.js:356
h @ backbone.js:155
c.trigger @ backbone.js:346
renderBody @ CanvasView.js:263
I @ underscore.js:762
(anonymous) @ underscore.js:775
(anonymous) @ underscore.js:122
(anonymous) @ jquery.min.js:2
Ie @ jquery.min.js:2
append @ jquery.min.js:2
addChild @ goldenlayout.min.js:2
_$onDrop @ goldenlayout.min.js:2
_onDrop @ goldenlayout.min.js:1
emit @ goldenlayout.min.js:1
onMouseUp @ goldenlayout.min.js:1
i @ jquery.min.js:2
dispatch @ jquery.min.js:2
v.handle @ jquery.min.js:2
load (async)
render @ CanvasView.js:488
render @ index.js:251
render @ EditorView.js:30
render @ index.js:761
init @ index.js:78
init_gjs @ main.js:5
(anonymous) @ jspanel.js:90
emit @ goldenlayout.min.js:1
init @ goldenlayout.min.js:1
e @ jquery.min.js:2
t @ jquery.min.js:2
setTimeout (async)
(anonymous) @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
fire @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
ready @ jquery.min.js:2
B @ jquery.min.js:2`