Convert OR / HR fields with empty string to None

[nebfield]

One scoring file in the Catalog(PGSXX4900-ish) has the OR field set to an empty string, which currently raises a validation error

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.61%. Comparing base (f570666) to head (7809c6c).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #57   +/-   ##
=======================================
  Coverage   89.61%   89.61%           
=======================================
  Files          54       54           
  Lines        3467     3467           
=======================================
  Hits         3107     3107           
  Misses        360      360           

Flag	Coverage Δ
pgscatalog.core	92.59% <ø> (ø)

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