[8.0](backport #29190) winlogbeat/sys/winevent: use reflect IsZero method

[mergify]

This is an automatic backport of pull request #29190 done by Mergify.

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[elasticmachine]

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• Start Time: 2021-11-30T11:33:33.498+0000

• Duration: 107 min 34 sec

• Commit: a9a6c0a

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Test	Results
Failed	0
Passed	41094
Skipped	4271
Total	45365

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