No matching function for call without non-parameter constructor

Question

We have a template class containing another class containing template object with parameterized constructor.

template<class T>
class A {
public:

    class B {
    public:
        T object;

        B(T obj) {
            this->object = obj;
        }
    };

    T foo(T obj) {
        B *b = new B(obj);
        return b->object;
    }
};

Also we have a class of object we want as foo() parameter:

class Item {
public:
    int value;

//  Item() {}
//  Non-parameter constructor. Within works fine

    Item(int value) {
        this->value = value;
    }
};

Notice: Within non-parameter constructor Item() {} code run flawlessly, but for some reason constructor always runs once without being called explicitly.

And here goes main() to call a.foo():

    A<Item> a;
    Item item(5);

    cout << a.foo(item).value;  //expected: 5

Eventually we got an error like this:

error: no matching function for call to 'Item::Item()'
    B(T obj) {
             ^

Question: How to made code with this structure work without having non-parameter constructor in Class Item {}?

• What is the reason of that structure?
• I code implementation of doubly linked list and simplified such error from it into this code above.

HINT: I want to make code work without changing Class Item {} definition because I'm provider of Class A and I want to resolve this case particularly.

SOLVED

Error solved by using member initialization list. Thanks to Ulrich Eckhardt.

B(T obj) {
    this->object = obj;
}
//wrong

B(T obj): object(obj) {}
//correct