fix(redis): preserve empty arrays in payload

[rrmesquita]

DISCLAIMER: Since I'm not too familiar with the codebase, this PR was AI assisted with Opus 4.8 high. Feel free to discard the PR — although I think the solution here makes sense.

[RomainLanz]

Thanks for sending this, the bug is real and the direction makes sense.

I think we need to take the fix a bit further before merging. This patch protects the popFrom() and getJob() return paths, but Redis still has other scripts that decode the stored job JSON and then write it back.

I would rather make the invariant explicit. user job JSON/payload should stay opaque to Lua, and any Lua-side mutable metadata should be handled without re-encoding the full job.

I'm going to take this on from our side because it touches a few Redis internals, but this PR helped identify the right problem. Thanks again for digging into it.