fix(hybridcloud): Handle null meta in RPC endpoint

request.data.get("meta", {}) returns None when the payload contains
"meta": null, since the default only applies for missing keys. Use
`or {}` to handle both missing and null values, preventing an
AttributeError on the subsequent .get() call.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gricha

src/sentry/api/endpoints/internal/rpc.py

@@ -64,7 +64,7 @@ def post(self, request: Request, service_name: str, method_name: str) -> Respons
                 sentry_sdk.capture_exception()
                 raise ParseError from e
 
-        meta = request.data.get("meta", {})
+        meta = request.data.get("meta") or {}
         vc_data = meta.get("viewer_context")
         vc_scope: contextlib.AbstractContextManager[None] = contextlib.nullcontext()
         if vc_data: