Make safari only break on fractions

Summary: Also, make errors on the initial parse not prevent further
parses.

Auditors: alpert

static/main.js

@@ -2,14 +2,14 @@ window.onload = function() {
     var input = document.getElementById("input");
     var math = document.getElementById("math");
 
-    reprocess();
-
     if ("oninput" in input) {
         input.addEventListener("input", reprocess, false);
     } else {
         input.attachEvent("onkeyup", reprocess);
     }
 
+    reprocess();
+
     function reprocess() {
         katex.process(input.value, math);
     }