MgSelectionBase returns NULL instead of empty collections for certain APIs

[jng]

In line 450 of SelectionBase.cpp (MgSelectionBase::GetLayers())

if (selLayers->GetCount() == 0)
{
   return NULL;
}

In line 482 of SelectionBase.cpp (MgSelectionBase::GetClasses(CREFSTRING layer))

if (strColl->GetCount() == 0)
{
    return NULL;
}

Shouldn't we just return the collection as-is? It will be empty anyway so consumers won't get anything from it.

[jng]

No point changing what's ingrained now.