Numpy array args in register

[StephenThornquist]

assign_reg_io accepts Optional[Union[ndarray,BinaryFile]] arguments, but the code checked simply used if arg, which raises an Exception for ndarray.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.32%. Comparing base (be8830d) to head (ecabf91).
⚠️ Report is 228 commits behind head on main.

Files with missing lines	Patch %	Lines
suite2p/registration/register.py	50.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1227      +/-   ##
==========================================
+ Coverage   55.21%   58.32%   +3.10%     
==========================================
  Files          43       47       +4     
  Lines        5055     4434     -621     
==========================================
- Hits         2791     2586     -205     
+ Misses       2264     1848     -416     

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[StephenThornquist]

Redundant with #1226, closing my PR