Fix "Uncaught Error: Call to a member function getStatusCode() on null" (#203)

The method "MessageSentReport::getStatusCode" now considers that its
"response" property can be null (because Guzzle can return null when
calling "RequestException::getResponse").

Author: steffenweber

src/MessageSentReport.php

@@ -109,6 +109,10 @@ public function getEndpoint(): string {
 	 * @return bool
 	 */
 	public function isSubscriptionExpired(): bool {
+		if (!$this->response) {
+			return false;
+		}
+
 		return \in_array($this->response->getStatusCode(), [404, 410], true);
 	}