Merge pull request #148 from vjuradouson/fix/avoid-expire-lifetime-null

Avoid expiration life time when $specificLifetime has not passed in f…

Author: colinmollenhour

Cm/Cache/Backend/Redis.php

@@ -543,7 +543,8 @@ public function save($data, $id, $tags = array(), $specificLifetime = false)
         else
             $tags = array_flip(array_flip($tags));
 
-        $lifetime = (int)$this->_getAutoExpiringLifetime($this->getLifetime($specificLifetime), $id);
+        $lifetime = $this->_getAutoExpiringLifetime($this->getLifetime($specificLifetime), $id);
+        $lifetime = $lifetime === null ? $lifetime : (int) $lifetime;
 
         if ($this->_useLua) {
             $sArgs = array(