Modal masks for multiple popups are not working

[MPulxeR]

When having multiple popups (Dialogs), the modal mask is "only" rendered correct on the first popup. When the second popup is opened ... the modal mask is not shown ... e.g.:

That leads to the problem, that the second popup is either not directly shown (without focus) ... or, it will be autoClosed or loosing its focus once the first popup is clicked.

Looking at the DOM, only one modal mask is rendered. However, expectation is each modal popup has its own modal mask.

Here is an example for CodePen.io:

import * as Module from 'https://bryntum.com/products/grid/build/grid.module.js';
Object.assign(window, Module);

new Button({
    appendTo : document.body,
    cls      : 'b-raised',
    text     : 'Show popup',
    onClick  : function(e) {
        let popup = new Popup({
            autoShow: false,
            autoClose: false,
            centered: true,
            modal: true,
            width: '60%',
            height: '60%',
            items: [new Button({
              text: 'open another modal popup',
              onClick: function(e) {
                var internalPopup = new Popup({
                  width: '40%',
                  height: '40%',
                  header: 'internal modal popup',
                  centered: true,
                  modal: true,
                  autoShow: false,
                  autoClose: false
                });
                internalPopup.show();
                internalPopup.focus();
              }
            })
            ]
        });
        popup.show();
    }
});