Inserted chart in WYSIWYG editor is not visible

Tested with XWiki 16.4.6:

• Edit a new page using WYSIWYG editor
• Insert a new macro
• Select chartjs
• use "pie" for the type and use values documented in https://extensions.xwiki.org/xwiki/bin/view/Extension/Chart.js%20Integration/#HExamples for the content
• Click submit

Expected result:

• the chart is inserted in the editor and immediately visible

Obtained result:

• a blank area is inserted, once clicking "Save & View" the result is propertly displayed, and further edition using the WYSIWYG editor do display properly the chart, it's even possible to change the type and obtain an immediate reload (try using line instead of pie)