fix the javascript version of the python bug too

Author: PierceLBrooks

js/src/javascript/tokenizer.js

@@ -371,7 +371,7 @@ Tokenizer.prototype._allow_regexp_or_xml = function(previous_token) {
   // regex and xml can only appear in specific locations during parsing
   return (previous_token.type === TOKEN.RESERVED && in_array(previous_token.text, ['return', 'case', 'throw', 'else', 'do', 'typeof', 'yield'])) ||
     (previous_token.type === TOKEN.END_EXPR && previous_token.text === ')' &&
-      previous_token.opened.previous.type === TOKEN.RESERVED && in_array(previous_token.opened.previous.text, ['if', 'while', 'for'])) ||
+      previous_token.opened && previous_token.opened.previous.type === TOKEN.RESERVED && in_array(previous_token.opened.previous.text, ['if', 'while', 'for'])) ||
     (in_array(previous_token.type, [TOKEN.COMMENT, TOKEN.START_EXPR, TOKEN.START_BLOCK, TOKEN.START,
       TOKEN.END_BLOCK, TOKEN.OPERATOR, TOKEN.EQUALS, TOKEN.EOF, TOKEN.SEMICOLON, TOKEN.COMMA
     ]));