[ENH] return input data if score is negative on first iter

[Randomidous]

• retain a copy of the input, which is returned if the mean_score is negative on iteration 0
• removed a couple trailing white spaces
• doesn't alter input data in place
• closes: Zapline: retain copy of input in case no artifact present #93

[nbara]

Thanks, I will make a PR to fix the CI first so we can merge this after

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.01%. Comparing base (ac12d71) to head (1bdbef5).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #94      +/-   ##
==========================================
+ Coverage   82.99%   83.01%   +0.01%     
==========================================
  Files          25       25              
  Lines        2829     2832       +3     
==========================================
+ Hits         2348     2351       +3     
  Misses        481      481              

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