[#165] Pass namespace argument

- Passes `$namespace` argument provided to `clearCurrentMessages()` to
  `hasCurrentMessages()` to ensure provided namespace is used when available.

library/Zend/Controller/Action/Helper/FlashMessenger.php

@@ -256,7 +256,7 @@ class Zend_Controller_Action_Helper_FlashMessenger extends Zend_Controller_Actio
             $namespace = $this->getNamespace();
         }
         
-        if ($this->hasCurrentMessages()) {
+        if ($this->hasCurrentMessages($namespace)) {
             unset(self::$_session->{$namespace});
             return true;
         }