local_shared_ptr have no assertions checks if operators "->" or "*" are called

local_shared_ptr:
```
typename boost::detail::sp_dereference< T >::type operator* () const noexcept
{
return *px;
}

typename boost::detail::sp_member_access< T >::type operator-> () const noexcept
{
return px;
}
```

shared_ptr have `BOOST_ASSERT( px != 0 );` before return.

I think it will be useful.