GetFirstDocTemplatePosition() returns NULL

Question

I have a MFC to display graph data. I created OCX for the same to display graph in another application. in Normal exe I have an right click pop up menu to do some operation. But when I use the OCX in another application, when I do right click application crash. I got the detail by debugging as follows,

POSITION  pos = AfxGetApp()->GetFirstDocTemplatePosition();
// here GetFirstDocTemplatePosition() returns NULL so the below line crashes.
CDocTemplate* doc_template = AfxGetApp()->GetNextDocTemplate(pos);

I couldn't understand why GetFirstDocTemplatePosition() returns NULL. I created separate MENU for exe and OCX. separate resource files too. Eg: My application is MyGraph then I created MyGraphOCX.sln for OCX and resource_ocx.h, MyGraphOCX.rc for OCX.

POSITION CWinApp::GetFirstDocTemplatePosition() const
{
    if (m_pDocManager == NULL)
        return NULL;
    return m_pDocManager->GetFirstDocTemplatePosition();
}

Here m_pDocManager is NULL. Why this is NULL I don't understand.

Please provide your valuable suggestions