MFC: How MDI Tabbed window works

Hi,

I have an application(MDI Tabbed) type.

I am facing the below described issue in tabbed documeent.

I have opened a single document(i.s a single tab is present in the frame). I hide the tab in my progamming. Then opened a new document, when i am trying to unhide the earlier tab by addTab API, it shows two tabs with same name and when closing it, it crashes.

Code:

 const CObList& tabGroups = pMainFrame->GetMDITabGroups();
          for (POSITION pos = tabGroups.GetHeadPosition(); NULL != pos;)
          {
           
            pNextTab = DYNAMIC_DOWNCAST(CMFCTabCtrl, tabGroups.GetNext(pos));
            ASSERT_VALID(pNextTab);
            if (NULL == pNextTab)
              continue;


            int nTabMaxIndx = pNextTab->GetTabsNum();
            for (int nTabCurrIndx = 0; nTabCurrIndx < nTabMaxIndx; ++nTabCurrIndx)
            {
      
              CMDIChildWndEx *pChildWnd = DYNAMIC_DOWNCAST(CMDIChildWndEx, pNextTab->GetTabWnd(nTabCurrIndx));
              ASSERT(pChildWnd);
              if (NULL == pChildWnd)
                continue;
  
              CWnd* pWnd = dynamic_cast<CView*> (pChildWnd->GetWindow(GW_CHILD));
              if ((NULL != pWnd) && (pWnd->m_hWnd == pTemplateView->m_hWnd))
              {

                // virtual BOOL ShowTab(int iTab, BOOL bShow = TRUE, BOOL bRecalcLayout 
                pNextTab->ShowTab(nTabCurrIndx, nCmdShow == SW_SHOWNORMAL ? TRUE : FALSE, TRUE, FALSE);
				bTabFound = true;
                break;
              }
            }
          }
        }/

		if((false == bTabFound) && (SW_SHOWNORMAL == nCmdShow))
		{
			pNextTab->AddTab(pWndTemplate, GetTitle(), (UINT)-1);
		}