Fail gracefully on empty template

Fixes #267

mustache.js

@@ -443,7 +443,7 @@ var Mustache;
       }
     }
 
-    return squashedTokens; 
+    return squashedTokens;
   }
 
   function escapeTags(tags) {
@@ -464,6 +464,7 @@ var Mustache;
    * course, the default is to use mustaches (i.e. Mustache.tags).
    */
   exports.parse = function (template, tags) {
+    template = template || '';
     tags = tags || exports.tags;
 
     var tagRes = escapeTags(tags);

test/parse_test.js

@@ -5,6 +5,7 @@ var Mustache = require('./../mustache');
 // A map of templates to their expected token output. Tokens are in the format:
 // [type, value, startIndex, endIndex].
 var expectations = {
+  ''                                        : [],
   '{{hi}}'                                  : [ [ 'name', 'hi', 0, 6 ] ],
   '{{hi.world}}'                            : [ [ 'name', 'hi.world', 0, 12 ] ],
   '{{hi . world}}'                          : [ [ 'name', 'hi . world', 0, 14 ] ],