Prevent empty annotation as first child of semantics element from producing an error.  Resolves issue #805.
Prevent empty annotation as first child of semantics element from producing an error.  Resolves issue #805.

thomasjm/MathJax,ManrajGrover/MathJax,thomasjm/MathJax,Ivanwangcy/MathJax,mcanthony/MathJax,mcanthony/MathJax,minrk/components-mathjax,wikimedia/MathJax,cben/MathJax,anusornc/MathJax,dpvc/MathJax,jeremykenedy/MathJax,physikerwelt/MathJax,nvp2211/MathJax,nvp2211/MathJax,GerHobbelt/MathJax,Edraak/MathJax,anusornc/MathJax,thomasjm/MathJax,GerHobbelt/MathJax,jinntrance/mathjax,ManrajGrover/MathJax,thomasjm/MathJax,cheerfulstoic/MathJax,cheerfulstoic/MathJax,anueshenxing/MathJax,rachetfoot/MathJax,perseoq/MathJax,minrk/mathjax-component,jinntrance/mathjax,Ivanwangcy/MathJax,thomasjm/MathJax,minrk/mathjax-component,jeremykenedy/MathJax,perseoq/MathJax,cben/MathJax,anueshenxing/MathJax,Edraak/MathJax,minrk/components-mathjax