Fix CSRF hash regeneration

For CSRF hash regeneration, $this->CSRFHash must be set to NULL when user set $this->CSRFRegenerate to TRUE, because in CSRFSetHash() you compare it with NULL, but $this->CSRFHash !== NULL after request.

Author: Workoverflow

system/Security/Security.php

@@ -221,6 +221,7 @@ public function CSRFVerify(RequestInterface $request)
 		if ($this->CSRFRegenerate)
 		{
 			// Nothing should last forever
+			$this->CSRFHash = null;
 			unset($_COOKIE[$this->CSRFCookieName]);
 		}