Error, can't find the script to get the value for the widget 's_xxx'

[RayPS]

What happened?

I was trying to add a setting to freq_fff.ui

https://user-images.githubusercontent.com/1941540/195408877-d971df92-3d7b-4812-b3e1-075cf827dd56.mp4

It seems working fine, except I'm always getting a warning of Error, can't find the script to get the value for the widget 's_xxx' at application startup.

Project file & How to reproduce

My freq_fff.ui

#logs
page:print:
group:freq_settings_event:no_title:no_search
	line:
		setting:simple:script:enum$none$None$bp$Support on build plate only$se$For support enforcers only$ev$Everywhere:depends$support_material$support_material_auto$support_material_buildplate_only:label$Supports:tooltip$Select what kind of support do you need:full_width:s_support_fff
		setting:simple:script:bool:depends$brim_width:label$Brim:tooltip$Set the brim. Will be set to 5mm if nothing was previously set.:s_brim
	end_line
	line:
		setting:label$Seam:width$8:full_width:script:enum$corners$Corners$nearest$Nearest$random$Scattered$allrandom$Random$aligned$Aligned$contiguous$Contiguous$rear$Rear$custom$Custom:depends$seam_position$seam_angle_cost$seam_travel_cost:s_seam_position
	end_line
	line:
		setting:label$Supporting dense layer:full_width:infill_dense
	end_line
	line:
		setting:label$No perimeters on bridge areas:sidetext$_:width$14:no_perimeter_unsupported_algo
	end_line
	line:
		setting:label$Fill the voids with bridges:sidetext$_:script:bool:s_bridge_void
	end_line
	line:
		setting:label$Infill:width$6:fill_density
		freq_purging_volumes
	end_line

My script under print.as

bool s_bridge_void_get()
{
	return get_int("no_perimeter_unsupported_algo") == 4;
}
void s_bridge_void_set(bool set)
{
	set_int("no_perimeter_unsupported_algo", set ? 4 : 0);
}

Version

2.4.58.5

Operating system

macOS 12.6

Printer model

E3V2

[RayPS]

By the way, I have extra questions:

1. What does freq_purging_volumes do?
2. Why is the label not showing up unless I have sidetext$_ or full_width