Fix GCC warnings
Fix GCC warnings

gstbdautil.cpp:388:66: warning: passing NULL to non-pointer argument 1 of ‘bool _com_ptr_t<_IIID>::operator==(int) [with _IIID = _com_IIID_getter<IPin, __IPin_IID_getter>]’ [-Wconversion-null]
gstbdautil.cpp:408:70: warning: passing NULL to non-pointer argument 1 of ‘bool _com_ptr_t<_IIID>::operator==(int) [with _IIID = _com_IIID_getter<IPin, __IPin_IID_getter>]’ [-Wconversion-null]

raipe/gst-bda