fix: 支付宝响应空签名时签名验证逻辑错误的问题

[lazychanger]

fix: #992 #975

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.40%. Comparing base (3683c69) to head (fc0681b).

❗ Current head fc0681b differs from pull request most recent head 6456456

Please upload reports for the commit 6456456 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #998   +/-   ##
=========================================
  Coverage     97.40%   97.40%           
- Complexity      907      909    +2     
=========================================
  Files           347      347           
  Lines          6202     6206    +4     
=========================================
+ Hits           6041     6045    +4     
  Misses          161      161           

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[yansongda]

@lazychanger 我优化了下，麻烦帮忙看看有啥问题没？

[lazychanger]

没问题
@yansongda