GDScript 2.0: getter of untyped variables can return nothing on some code paths

[mieldepoche]

Godot version

4.0.alpha12

System information

linux

Issue description

Getters have to return something explicitely in each code path.
This check if not performed for getters of untyped variables:

# raises an error in the editor
var x: int:
    get:
        pass

# does not
var y:
    get:
        pass

Steps to reproduce

see above

Minimal reproduction project

No response

[akien-mga]

Still reproducible in 4.0 RC 1.