EMSI Containers and HashMap of HashMaps

[Tobias Pankrath via Digitalmars-d-learn]

The following code segfaults, when the outer hashmap rehashes,
and I am not yet sure why.
```d
module tests.refcounted_hashmap_test;

import containers;
import std.typecons;

struct Map
{
    HashMap!(int, int) theMap;
}

unittest
{
    HashMap!(int, RefCounted!Map) mapOfMaps;
    foreach (i; 0 .. 1000)
    {
        RefCounted!Map val;
        if (i == 0) val.theMap.getOrAdd(i, i);
        mapOfMaps.getOrAdd(i, val);
    }
}
```

For your convenience: https://run.dlang.io/is/gHSlu1

I am using Refcounted() because HashMap itself is not copy-able. 
Is there another way to have HashMaps as values of HashMaps?