Segfault when using static with None values.

```
struct Test {
    m: Option<~str>
}

static DEFAULT: Test = Test{m: None};

struct Test2 {
    m: int
}

static DEFAULT2: Test2 = Test2{m: 1};

fn testing(a: Test) {
    println("Called");
}

fn testing2(a: Test2) {
    println("Called");
}

fn main() {
    testing2(DEFAULT2); // Prints
    testing(DEFAULT); //Segfault
}
```
