fix: credential error message bug

[PeterChen13579]

fixes #1737

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.10%. Comparing base (815dfd6) to head (56eb8cf).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1738      +/-   ##
===========================================
+ Coverage    72.08%   72.10%   +0.02%     
===========================================
  Files          287      287              
  Lines        12157    12160       +3     
  Branches      6177     6177              
===========================================
+ Hits          8763     8768       +5     
  Misses        1783     1783              
+ Partials      1611     1609       -2     

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[godexsoft]

@PeterChen13579 assuming that the output needs to match the same handler in rippled, don't they have an error code we can reuse in the latest libxrpl for this?