Subject of the issue

When I try to add a new widget in one column, it will reset all the nodes in one modal and doesn't change back them the correct position in multiple columns mode.

Steps to reproduce

1. start the gridstack.js angular example, and select component ngFor example.
2. Add 3 widgets.
3. Change the chrome width and make the widget show in one column.
4. Add a widget and change the chrome width to back multiple columns mode.

Expected behavior

The 3 widgets should be at the top.

Actual behavior

The 3 widgets at the left.