Use jQuery remove to remove children row elements

We can not rely on the row node to always have a parent node as toggle_row is
a callback to an event that can be executed after the row has already be
removed from the DOM.

Closes #13198

sao/src/view/tree.js

@@ -1787,8 +1787,7 @@
         collapse_children: function() {
             for (const row of this.rows) {
                 row.collapse_children();
-                var node = row.el[0];
-                node.parentNode.removeChild(node);
+                row.el.remove();
             }
             this.rows = [];
         },