title: Async.whilst inside async.series
body: <p>I am using <code>async.waterfall</code> inside <code>async.whilst</code>, inside <code>async.series</code> like this (which only crashes once, but then continues as it should):</p>
  
  <pre><code>function(callback){
  
   async.whilst(
    function() { 
     console.log("Number of things left: " + classes.length); return classes.length &gt; 0; 
    }, 
    function(innerCallback){
      //Define some variables.
  
      async.waterfall([
       function (next) {
        MyTable.find({ Data: theData},{ DataThis:1, Stuff:1, _id:0 },next).limit(1);
       },
       function (results, next) {
        if(results.length &gt; 0 &amp;&amp; results[0].theData=== parseInt(theInfo)){
         //Update my database
        } else{
         next();
        } 
       }
      ], setTimeout(function() { 
         //Splice the data. I.e. mydata.splice(i-1,1);                                            
         innerCallback(); 
      }, 0)); //closing async.waterfall.                      
    },
    function(err){
      // The final function of whilst 
      callback(err);
   }) // Whilst finished
  }
  </code></pre>
  
  <p>But I get an error:</p>
  
  <pre><code>serverClasses2-3 TypeError: undefined is not a function
  serverClasses2-3     at /home/node_modules/async/lib/async.js:52:16
  serverClasses2-3     at /home/node_modules/async/lib/async.js:1204:30
  serverClasses2-3     at /home/routes/indexClasses2.js:267:11
  serverClasses2-3     at Query.callback (/home/node_modules/mongoose/lib/query.js:2021:7)
  serverClasses2-3     at /home/node_modules/mongoose/node_modules/kareem/index.js:177:19
  serverClasses2-3     at /home/node_modules/mongoose/node_modules/kareem/index.js:109:16
  serverClasses2-3     at process._tickDomainCallback (node.js:381:11)
  </code></pre>
  
  <p>Have anyone encountered the same error? </p>