XS: Reflect property-key methods throw when propertyKey is omitted

[d01c2]

Build environment: macOS 26.5.2

Moddable SDK version:

• Installed via jsvu, so there is no SDK source tree / git describe.
• Engine reports: XS 17.9.1, slot 32 bytes, ID 4 bytes

Target device: desktop (host xs)

Description
Reflect.get throws when the propertyKey argument is omitted. The same behavior occurs with Reflect.has, Reflect.deleteProperty, Reflect.getOwnPropertyDescriptor, and Reflect.set.

An omitted argument supplies undefined. ToPropertyKey converts undefined to the String "undefined", so these methods should behave as if undefined were passed explicitly.

Steps to Reproduce

$ xst -e "Reflect.get([]);"
TypeError: no key (in Reflect.get)

Expected behavior
undefined is returned without an exception.

For comparison, V8 (15.3.27):

$ v8 -e "print(String(Reflect.get([])))"
undefined

Other information
XS already produces the expected result when undefined is passed explicitly:

$ xst -e "print(String(Reflect.get([], undefined)))"
undefined