500 Internal server error when expiring compressed document with only system XATTRs

CBS Version : 5.5.5-4505, 6.0.2-2407, 6.5.0-3394

SGW Version : 2.5.0-271

Steps to reproduce : 

1. Enable bucket compression on Couchbase Server
2. Start Sync Gateway with shared_bucket_access=enabled, import=true
3. Add a document to the bucket with a short expiry.
4. Document will be imported as rev 1- by Sync Gateway
5. Wait for document to expire
6. Document should be imported as tombstone rev 2-
7. Get the raw doc from Sync Gateway.

Actual :

Getting 500 Internal error

Expected :

Should get raw doc successfully

CBS logs : cbcollect_kv_500.zip

SGW logs: sgcollect_kv_500.zip

This is subsequent bug for https://issues.couchbase.com/browse/MB-34346