Method stack_reference

Libs/sol/sol.hpp:8860–8860

	public:
		stack_reference() noexcept = default;
		stack_reference(lua_nil_t) noexcept
		: stack_reference() {};
		stack_reference(lua_State* L, lua_nil_t) noexcept : stateless_stack_reference(L, 0), luastate(L) {