fix fetch() message 'ending' for multiple messages

lib/imap.js

@@ -228,10 +228,10 @@ ImapConnection.prototype.connect = function(loginCb) {
   function emitMsgEnd(key) {
     var fetches = requests[0].fetchers[key];
     for (var i=0, len=fetches.length; i<len; ++i) {
-      if (fetches[i]._msg._ended)
+      if (fetches[i]._msg) {
-        continue;
         fetches[i]._msg.emit('end');
-      fetches[i]._msg._ended = true;
+        fetches[i]._msg = undefined;
+      }
     }
   }