refactor: return nil when error has already been checked

[tgolang]

Description of change

Since we have already checked err before and returned when err != nil, err must be nil here.

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• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix

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Change checklist

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• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have selected the develop branch as the target branch
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• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
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