Non-capturing regex, don't catch some exceptions

Auditors: alpert

Lexer.js

@@ -26,7 +26,7 @@ var normals = [
 ];
 
 // Build a regex to easily parse the functions
-var anyFunc = /^\\([a-zA-Z]+|.)/;
+var anyFunc = /^\\(?:[a-zA-Z]+|.)/;
 
 // Lex a single token
 Lexer.prototype.lex = function(pos) {

katex.js

@@ -137,16 +137,16 @@ var clearNode = function(node) {
 var process = function(toParse, baseElem) {
     try {
         var tree = parseTree(toParse);
-        clearNode(baseElem);
-        var expression = buildExpression(tree);
-        for (var i = 0; i < expression.length; i++) {
-            baseElem.appendChild(expression[i]);
-        }
-        return true;
     } catch (e) {
         console.error(e);
         return false;
     }
+    clearNode(baseElem);
+    var expression = buildExpression(tree);
+    for (var i = 0; i < expression.length; i++) {
+        baseElem.appendChild(expression[i]);
+    }
+    return true;
 };
 
 module.exports = {