[Issue 19691] ICE on null default value for struct parameter in constructor

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19691

--- Comment #2 from Basile-z <b2.temp at gmx.com> ---
reduced : 

module b19691;

struct S1
{
    this(T)(T)
    {
        S2("");
    }
}

struct S2
{
    this(S1 s = ""){}
}

--