From c4627ff8ca4ae8d27fd3d5d6a9b708633f225d3b Mon Sep 17 00:00:00 2001
From: "Davide P. Cervone" <dpvc@union.edu>
Date: Thu, 13 Jun 2019 11:15:21 -0400
Subject: [PATCH] Check that svg and html elements exist before trying to use
 them (in case the input jax fails).  See issue #441.

---
 lib/main.js | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/lib/main.js b/lib/main.js
index 073a9e94..dd2a0593 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -620,6 +620,7 @@ function AddError(message,nopush) {
 function GetMML(result) {
   if (!data.mml && !data.mmlNode) return;
   var jax = MathJax.Hub.getAllJax()[0];
+  if (!jax) return;
   if (data.speakText && !jax.root.alttext) {
     jax.root.alttext = result.speakText;
     var attrNames = jax.root.attrNames;
@@ -643,10 +644,11 @@ function GetMML(result) {
 function GetSpeech(result) {
   if (!data.speakText) return;
   result.speakText = "Equation";
-  if (data.format !== "MathML") result.speakText = data.math;
-  else {
+  if (data.format !== "MathML") {
+    result.speakText = data.math;
+  } else {
     var jax = MathJax.Hub.getAllJax()[0];
-    if (jax.root.alttext) result.speakText = jax.root.alttext;
+    if (jax && jax.root.alttext) result.speakText = jax.root.alttext;
   }
 }
 
@@ -658,7 +660,7 @@ function GetHTML(result) {
   if (!data.html && !data.htmlNode) return;
   var jax = MathJax.Hub.getAllJax()[0]; if (!jax) return;
   var script = jax.SourceElement(), html = script.previousSibling;
-
+  if (!html) return;
   // add speech text if there isn't one
   if (data.speakText){
     var labelTarget = html.querySelector('.mjx-math');
@@ -695,6 +697,7 @@ function GetSVG(result) {
   var jax = MathJax.Hub.getAllJax()[0]; if (!jax) return;
   var script = jax.SourceElement(),
       svg = script.previousSibling.getElementsByTagName("svg")[0];
+  if (!svg) return;
   svg.setAttribute("xmlns","http://www.w3.org/2000/svg");
 
   //