Hey,
First of, you can utilize g_form.getReference() for this, which is way easier. A great blog about this can be found here.
As to why your script does not work:
My assumption is the return of the guser GlideRecord. Here you don't just return the result you want, but the full glide record. I assume, that this causes some issues. Rather put the result in a separate object in your script include and return it as a simple object.
Regards
Fabian
