desirable.
By default these errors are logged to the console and in the QGIS UI.
But for some operations errors are expected and logging these just results
in noise.
For the c++ api dox this expands to "\c nullptr" (the
\c directive indicates a code literal value), and for sipify/Python
it expands to ``None`` (`` is sphinx annotation for literal values)
Makes for nicer dox for both c++ and Python!
