improve credentials null check

[JacksonTian]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.75000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 81.88%. Comparing base (81b66b7) to head (b3b8225).

Files with missing lines	Patch %	Lines
python/alibabacloud_tea_openapi/client.py	87.50%	2 Missing ⚠️
ts/src/client.ts	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #168      +/-   ##
==========================================
+ Coverage   81.13%   81.88%   +0.75%     
==========================================
  Files           5        5              
  Lines        3149     3197      +48     
  Branches      114      118       +4     
==========================================
+ Hits         2555     2618      +63     
+ Misses        518      503      -15     
  Partials       76       76              

Flag	Coverage Δ
golang	76.88% <100.00%> (+0.44%)	⬆️
python	83.69% <87.50%> (+1.35%)	⬆️
typescript	89.22% <87.50%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.