perf: optimise set_cors_headers (bp #12460) (#12462)

(cherry picked from commit 68c6fc4a44)

Co-authored-by: Sagar Vora <sagar@resilient.tech>

frappe/app.py

@@ -152,10 +152,10 @@ def process_response(response):
 
 def set_cors_headers(response):
 	origin = frappe.request.headers.get('Origin')
-	if not origin:
+	allow_cors = frappe.conf.allow_cors
+	if not (origin and allow_cors):
 		return
 
-	allow_cors = frappe.conf.allow_cors
 	if allow_cors != "*":
 		if not isinstance(allow_cors, list):
 			allow_cors = [allow_cors]