feat: revert to `null` in response

[soedirgo]

To make it consistent with other client libs. Will decide on null vs. undefined in response for supabase-js v3.

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:tada: This PR is included in version 1.0.0-rc.6 :tada:

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• npm package (@rc dist-tag)

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[github-actions[bot]]

:tada: This PR is included in version 1.0.0 :tada:

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

Your semantic-release bot :package::rocket: