gdb: scylla sstables: Fix for older versions of GDB
gdb: scylla sstables: Fix for older versions of GDB

Some GDB versions complain about subscript being a gdb.Value

Reviewed-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <ce3d91779be043b822ba6f250e488933b0fdea33@scylladb.com>

scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla