stage1: fix case close to 8520

[g-w1]

Fix a case close to #8520.

const expect = @import("std").testing.expect;
const Empty = struct {
    pub const PI = 3.14;
    pub const PI2: u32 = undefined;
};
test "struct namespaced variable" {
    expect(Empty.PI == 3.14);
    expect(Empty.PI2 == 3.14); // fails to fail
    expect(@sizeOf(Empty) == 0);

    // you can still instantiate an empty struct
    const does_nothing = Empty{};
}

Note: without the u32 type annotation here, it does not work.

[g-w1]

I think this is a bug that has a bigger root and this is a bad fix, closing.