Cannot convert argument 1 from 'Work' to std::nullptr_t

I'm trying to convert a String to a uint8 vector contained in a shared_ptr but am currently getting the Cannot convert argument 1 from 'Work' to std::nullptr_t error from my compiler. I'm quite new to C++ and this type of workflow is needed if possible.

std::string data = "Hello";
std::vector<uint8_t> vec(data.begin(), data.end());

typedef std::vector<uint8_t> Strang;
Strang str(vec);

typedef std::shared_ptr<Strang> Data;
Data d(str);