check for valid start state in tokenizer

lib/ace/tokenizer.js

@@ -222,6 +222,10 @@ var Tokenizer = function(rules) {
 
         var currentState = startState || "start";
         var state = this.states[currentState];
+        if (!state) {
+            currentState = "start";
+            state = this.states[currentState];
+        }
         var mapping = this.matchMappings[currentState];
         var re = this.regExps[currentState];
         re.lastIndex = 0;