bugfix: patch pod image fail when gs image is nil

[chrisliu1995]

No description provided.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5a15888) 35.47% compared to head (32a88e2) 35.55%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #121      +/-   ##
==========================================
+ Coverage   35.47%   35.55%   +0.08%     
==========================================
  Files          26       26              
  Lines        3538     3535       -3     
==========================================
+ Hits         1255     1257       +2     
+ Misses       2217     2213       -4     
+ Partials       66       65       -1     

Flag	Coverage Δ
unittests	35.55% <100.00%> (+0.08%)	⬆️

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[ringtail]

/LGTM