svg_view: avoid a crash in case of NULL x or y parameter in _show_text
svg_view: avoid a crash in case of NULL x or y parameter in _show_text

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