Active Qt qaxserverbase missing an error check in getConnectionInterface

According to ms documentation the function STDMETHOD(GetConnectionInterface)(IID *pIID) in qaxserverbase.cpp should check if the input is null or invalid and return E_POINTER in such case.

Currently no checks are performed and any pIID value would cause the function to return S_OK.

Refer to https://msdn.microsoft.com/en-us/windows/desktop/ms693468