This happens in both squid and main on objects that are larger enough to have tail rados objects (>4MB).
Reproducer:

    start a vstart cluster
    do the following on client side

    $ s3cmd -c s3cfg.vstart --host=http://localhost:8000 mb s3://bar
    $ s3cmd -c s3cfg.vstart --host=http://localhost:8000 put ../test_files/file_10m s3://bar/file_10m
    $ aws s3api --profile vstart --endpoint=http://localhost:8000 copy-object --copy-source bar/file_10m --key file_10m --bucket bar --metadata-directive "REPLACE" --content-type "text/plain" 

    in vstart

    $ bin/radosgw-admin -n client.rgw.8000 gc process --include-all

    on client side

    $ aws s3api --profile vstart --endpoint=http://localhost:8000 head-object --key file_10m --bucket bar
    {
        "AcceptRanges": "bytes",
        "LastModified": "2025-04-01T13:30:03+00:00",
        "ContentLength": 10485760,
        "ETag": "\"1e1d3a01dfedd497cbdd0ca9a39b1e72-2\"",
        "ContentType": "text/plain",
        "Metadata": {},
        "PartsCount": 2
    }

    $ aws s3api --profile vstart --endpoint=http://localhost:8000 get-object --key file_10m --bucket bar file_10m
    argument of type 'NoneType' is not iterable


    get-object fails with "NoSuchKey".