Fix arrayReduce with nullable aggregate function name

[Algunenano]

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• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

• Fix arrayReduce with nullable aggregate function name

Documentation entry for user-facing changes

Closes #59600

[robot-clickhouse-ci-1]

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[Algunenano]

Need to apply the same for LowCardinality -> SELECT arrayReduce(toLowCardinality('median'), [toLowCardinality(toNullable(8))])