[7.16](backport #28872) fix: use array length properly

[mergify]

This is an automatic backport of pull request #28872 done by Mergify.

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💔 Build Failed

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• Start Time: 2021-11-09T08:50:12.215+0000

• Duration: 6 min 31 sec

• Commit: c14bccb

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• Took 0 min 0 sec . View more details here
• Description: git diff --name-only origin/7.16...c14bccb92217b744b9d3d622200b3f3378077a56 > git-diff.txt

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