B4J Question [banano] [sithasodaisy] Uncaught (in promise) TypeError: Cannot read properties of null (reading 'append')

[giannimaione]

hello,
attach file with a demo;
i want build page with sithasodaisy, via code without Internal Design - abstract designer
log error:

'Uncaught (in promise) TypeError: Cannot read properties of null (reading 'append')
Log("start build page")
    page.Root.DesignMode(False)
    Log("center the page container")
    page.Root.MXAuto
    Log("add 5 rows, each having 2 columns, each spanning 6")
    page.Root.AddRows5.AddColumns12
  
    Log("build the grid")
    ' Uncaught (in promise) TypeError: Cannot read properties of null (reading 'append')
    page.Root.BuildGrid

any help ?