Fix data type check for padding short complex pings

[ctuguinay]

When testing SWFSC RAW files, there was a file where range was adaptive and based on bottom. When open_raw is called, these pings need to be padded because they are short and non-uniform with the other short pings. In this padding code, there was a snippet that relied on complex_ to work, but complex_ is complex128, while our data is complex64. I changed this to instead use complex64.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.81%. Comparing base (9f56124) to head (26ecb36).
Report is 119 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1353      +/-   ##
==========================================
- Coverage   83.52%   78.81%   -4.71%     
==========================================
  Files          64       16      -48     
  Lines        5686     2700    -2986     
==========================================
- Hits         4749     2128    -2621     
+ Misses        937      572     -365     

Flag	Coverage Δ
unittests	78.81% <100.00%> (-4.71%)	⬇️

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[leewujung]

Thanks @ctuguinay for the diagnosis and quick fix!