Handle null tuple for redisearch document

[jjsimps]

Description

Recently, I updated to the latest version of RediSearch (2.10.7). I started getting a particular error that originates from within the redisearch library:

Cannot read properties of null (reading 'length') TypeError: Cannot read properties of null (reading 'length')
    at documentValue (/app/node_modules/.pnpm/@redis+search@1.2.0_@redis+client@1.6.0/node_modules/@redis/search/dist/commands/SEARCH.js:29:23)
    at Object.transformReply (/app/node_modules/.pnpm/@redis+search@1.2.0_@redis+client@1.6.0/node_modules/@redis/search/dist/commands/SEARCH.js:17:61)
    at transformCommandReply (/app/node_modules/.pnpm/@redis+client@1.6.0/node_modules/@redis/client/dist/lib/commander.js:89:20)
    at Commander.commandsExecutor (/app/node_modules/.pnpm/@redis+client@1.6.0/node_modules/@redis/client/dist/lib/client/index.js:190:54)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

This error seems to have originated from this change. Instead of returning an empty array [], None is returned. The library does not handle this case, and so the error is thrown.

This PR checks if the document is NULL, and if it is, return the object. This would give the same behavior as before.

I encountered this in the latest redis version (4.7). Not sure which branch I should be comitting to.

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Checklist

• Does npm test pass with this change (including linting)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?