Update MessageParser.php

fix :

check value at index 1 for prevent php notice :

PHP Notice: Undefined offset: 1 in guzzle\parser\Guzzle\Parser\Message\MessageParser.php on line 36

Notice: Undefined offset: 1 in guzzle\parser\Guzzle\Parser\Message\MessageParser.php on line 36
Merge pull request #41 from PouyaDarabi/master

Update MessageParser.php