address review comments; part of #207

Author: pkra

lib/main.js

@@ -597,11 +597,11 @@ function GetSVG(result) {
     // Note: if aria-label exists, getSpeech preserved it in speakText
     // remove aria-label since labelled-by desc is preferred
     svg.removeAttribute("aria-label");
+    ID++; var id = "MathJax-SVG-"+ID+"-Desc";
+    svg.setAttribute("aria-labelledby",id);
+    var node = MathJax.HTML.Element("desc",{id:id},[result.speakText]);
+    svg.insertBefore(node,svg.firstChild);
   }
-  ID++; var id = "MathJax-SVG-"+ID+"-Desc";
-  svg.setAttribute("aria-labelledby",id);
-  var node = MathJax.HTML.Element("desc",{id:id},[result.speakText]);
-  svg.insertBefore(node,svg.firstChild);
 
   if (data.svg){
     //