How to replace icon with specified size?

Hi all!
I have the folowing initialization code:

pControl->GetImageManager()->SetIcon(hicon,pControl->GetID(),CSize(16,16));

How can I replace this icon with new one with same size?
When I try to use the same way to replace the old icon, there is an assert at Line 2379 in file xtpimagemanager.cpp. I found in help the metod RemoveIcon. But this metod removes all icons for the specified control.

My version of Xtreme Toolkit Pro is 10.3.1. And the code is:

CXTPImageManagerIcon* CXTPImageManagerIconSet::CreateIcon(UINT nWidth)
{
    CXTPImageManagerIcon* pIcon = 0;
    if (m_mapIcons.Lookup(nWidth, pIcon))
    {
        ASSERT(pIcon->m_nID == m_nID);
        ASSERT(pIcon->m_nWidth == nWidth); // line 2379
    }
    else
    {
         ........
    }

    ASSERT(pIcon);

    return pIcon;
}