Missing correct unit for via_count constaint in Custom Design Rule

Description

There is no correct unit for via_count constraint in Custom Design Rule. The error says ERROR: Missing units for 'x' (must be mm, in, or mil).

Steps to reproduce

1. Open the Custom Design Rule panel File > Board Setup > Design Rules > Custom Rules.
2. Type a rule with via_count constraint.
3. Click "Check rule syntax" button.

KiCad Version

Application: KiCad PCB Editor (64-bit)

Version: (6.0.9), release build

Libraries:
	wxWidgets 3.2.1
	libcurl/7.83.1-DEV Schannel zlib/1.2.12

Platform: Windows 10 (build 19044), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Oct 29 2022 23:44:28
	wxWidgets: 3.2.1 (wchar_t,wx containers)
	Boost: 1.79.0
	OCC: 7.6.0
	Curl: 7.83.1-DEV
	ngspice: 37
	Compiler: Visual C++ 1929 without C++ ABI

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON