fix(webhook): r is referenced here before its initialized

Broke in #21064

Sentry: FRAPPE-2SH

Signed-off-by: Akhil Narang <me@akhilnarang.dev>
(cherry picked from commit 2af42f5)

frappe/integrations/doctype/webhook/webhook.py

@@ -156,7 +156,7 @@ def get_context(doc):
 
 
 def enqueue_webhook(doc, webhook) -> None:
-	request_url = headers = data = None
+	request_url = headers = data = r = None
 	try:
 		webhook: Webhook = frappe.get_doc("Webhook", webhook.get("name"))
 		request_url = webhook.request_url