Merge pull request #38261 from tanshanshan/more-readable
Automatic merge from submit-queue (batch tested with PRs 37701, 36702, 37145, 37424, 38261)
replace err with nil when err is nil
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**What this PR does / why we need it**:
When err is nil ,replace err with nil, that can make code more readable
Thanks.
**Special notes for your reviewer**:
**Release note**:
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ae1a7784af