fix(webhooks): fix crash when headers is null with header auth method

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

apps/webhooks/lib/BackgroundJobs/WebhookCall.php

@@ -32,7 +32,7 @@ class WebhookCall extends QueuedJob {
 		$client = $this->clientService->newClient();
 		$options = [];
 		$options['body'] = json_encode($data);
-		$options['headers'] = $webhookListener->getHeaders();
+		$options['headers'] = $webhookListener->getHeaders() ?? [];
 		try {
 			switch ($webhookListener->getAuthMethodEnum()) {
 				case AuthMethod::None:

apps/webhooks/lib/Db/WebhookListener.php

@@ -15,6 +15,7 @@ use OCP\Security\ICrypto;
 /**
  * @method void setUserId(string $userId)
  * @method string getUserId()
+ * @method ?array getHeaders()
  */
 class WebhookListener extends Entity implements \JsonSerializable {
 	/** @var ?string id of the app_api application who added the webhook listener */