Fix empty result from xread_options with deleted entries

[Quiwin]

Hello!

xread_options seems to not handle correctly case when a pending message is deleted.

In my understanding, if a pending message is deleted, its id should still be returned https://redis.io/commands/xreadgroup/#what-happens-when-a-pending-message-is-deleted

This is useful for acknowledging them and cleaning the PEL if some messages could not be processed.

Expected vs actual result

The expected result from the test case is:

&result_deleted_entry = StreamReadReply {
    keys: [
        StreamKey {
            key: "k1",
            ids: [
                StreamId {
                    id: "1666711514590-0",
                    map: {},
                },
            ],
        },
    ],
}

On redis-rs 0.20.2:

&result_deleted_entry = StreamReadReply {
    keys: [
        StreamKey {
            key: "k1",
            ids: [],
        },
    ],
}

On main an Err is thrown:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Response was of incompatible type: "Response type not hashmap compatible" (response was nil)', redis/tests/test_streams.rs:393:10

This is fixed by converting a nil value from redis when casting as an hash into a empty hash.

I am open to better solutions/suggestions!

[djc]

I'm confused why you mention version 0.20.2. Is this a regression, or were you just using a really old version before?

[Quiwin]

We were using a old version but the issue is also present on main.

[jaymell]

Thanks for the PR!