修复Bug-脱敏时未处理None（数据库的null）问题，导致结果为字符串的'None'。

[feiazifeiazi]

如题。

修复前：

修复后：

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.35%. Comparing base (8d96dc2) to head (f3eda58).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2880   +/-   ##
=======================================
  Coverage   78.35%   78.35%           
=======================================
  Files         124      124           
  Lines       17580    17582    +2     
=======================================
+ Hits        13775    13777    +2     
  Misses       3805     3805           

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[feiazifeiazi]

@LeoQuote 这个PR也给看看？