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

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

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• Start Time: 2021-11-09T08:49:39.699+0000

• Duration: 116 min 28 sec

• Commit: 247cd95

Test stats 🧪

Test	Results
Failed	0
Passed	53174
Skipped	5289
Total	58463

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