BUGFIX: Fix compile time error handling exception

Fix for the following fatal error during compile time execution:

    PHP Fatal error:  Uncaught Error: Call to a member function captureException() on null in .../neos/Data/Temporary/Production/Cache/Code/Flow_Object_Classes/Networkteam_SentryClient_ErrorHandler.php:69

Author: hlubek

Classes/Networkteam/SentryClient/ErrorHandler.php

@@ -44,6 +44,9 @@ public function initializeObject() {
 	 * @param array $extraData Additional data passed to the Sentry sample
 	 */
 	public function handleException($exception, array $extraData = array()) {
+		if (!$this->client instanceof \Raven_Client) {
+			return;
+		}
 
 		if (!$exception instanceof \Exception) {
 			if ($exception instanceof \Throwable) {