[ISSUE #4424] Fixed issue where null values could not be converted to base parameters

[neighbor-uncleWang]

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What is the purpose of the change

修复#4424

Brief changelog

当protectThreshold传入值为null时，给它设置一个默认值。

Verifying this change

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[KomachiSion]

Thanks @neighbor-uncleWang . Looking forward to more contributions