Add missing const.
Add missing const.

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