It looks like this check fails on GCC 4.9 per Marshall's commit message. We should revisit why and perhaps conditionally enable this assert.

```
    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
    basic_string_view(const _CharT* __s, size_type __len) _NOEXCEPT
        : __data(__s), __size(__len)
    {
// #if _LIBCPP_STD_VER > 11
//         _LIBCPP_ASSERT(__len == 0 || __s != nullptr, "string_view::string_view(_CharT *, size_t): received nullptr");
// #endif
    }
```