Router Fixed An Issue When Handling Http 303

Fix: CVE-2026-47221 <https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr>_

Fixed an issue when handling HTTP 303 internal redirects for body-less requests. The redirect handling code attempted to drain a request body buffer that was never allocated, causing a segmentation fault.