Page size selector is duplicated when xwiki:livetable:loading is triggered

This can be easily reproduced using the following code, excuted in a page containing a livetable:

require(['jquery', 'xwiki-events-bridge'], function($) {
  $(document).trigger('xwiki:livetable:loading');
});

The issue seems to be at https://github.com/xwiki/xwiki-platform/blob/ed89b3c1a8559852846c0e41d312d4204b458620/xwiki-platform-core/xwiki-platform-web/src/main/webapp/resources/js/xwiki/table/livetable.js#L873 where there is no checking for existing child before creating a new one.