Description:
------------
When using the set-function of the Memcache-package and do not define the key you want to set a certain value to, the package incorrectly uses the value-length as a key.

Reproduce code:
---------------
<?
  $mc = new memcached;
  $value = array("foo" => "bar");
  $mc->set($undefined_key, $value);
?>





Expected result:
----------------
Memcache should do nothing at all, since the defined keyname is null.

Actual result:
--------------
<10 new client connection
<10 set  1 1164711401 26
>10 CLIENT_ERROR bad command line format
<10 a:1:{s:3:"foo";s:3:"bar";}
>10 ERROR
<10 connection closed.