null check mathjax

services/web/public/coffee/ide/chat/directives/mathjax.coffee

@@ -15,12 +15,12 @@ define [
 			processEscapes: true
 		skipStartupTypeset: true
 
-	MathJax.Hub.Config(mathjaxConfig);
+	MathJax?.Hub?.Config(mathjaxConfig);
 	
 	App.directive "mathjax", () ->
 		return {
 			link: (scope, element, attrs) ->
 				setTimeout () ->
-					MathJax.Hub.Queue(["Typeset", MathJax.Hub, element.get(0)])
+					MathJax?.Hub?.Queue(["Typeset", MathJax?.Hub, element.get(0)])
 				, 0
 		}