C++ Heterogeneous container memory (?) problem (return 0xC0000005)

My assignment is to make a template class for store heterogeneous collections. There is a test code for the assignment and I have some problem with the 4th test.

Here is the template class: https://imgur.com/rx3yRy0

Here is the testclass: https://imgur.com/i58s0eX

/// The problematic test part: Checking the Traverse

TEST(Test4, heterogen) {
    HeteroStore<TestClass> t1;
    t1.add(new TestClass1(1));
    t1.add(new TestClass1(2));
    t1.add(new TestClass2("Hello"));
    t1.add(new TestClass2("World"));
    t1.add(new TestClass1(3));
    t1.add(new TestClass2("Bye"));
    std::stringstream ss;
    TestClassPrint print(ss);
    t1.traverse(print);  //This is where the program stops working
} 

///The template function

template<class func>
void traverse(func F)const{
for (size_t i=0; i<db; i++)
    if (t[i]!=NULL)
        F(t[0]);
    }

The output: https://imgur.com/uHrhRMj