dom_node: check the validity of the new child parameter.
dom_node: check the validity of the new child parameter.

janmarthedal/mathml2svg,janmarthedal/mathml2svg,janmarthedal/mathml2svg,gjtorikian/lasem,gjtorikian/lasem,gjtorikian/lasem,wavewave/lasem,gjtorikian/lasem,wavewave/lasem,janmarthedal/mathml2svg,wavewave/lasem,wavewave/lasem