Correctly handle parameters with empty lists as values

[GDYendell]

Fixes #30

>>> dbgrep("*Error*")
...
ODIN-118:EF:0StatusError
ODIN-118:FP:FP0:Error
ODIN-118:FP:FP1:Error
ODIN-118:FP:FP2:Error
ODIN-118:FP:FP3:Error
ODIN-118:MW:0StatusError

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.38%. Comparing base (c213f25) to head (7467e1e).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #31   +/-   ##
=======================================
  Coverage   81.38%   81.38%           
=======================================
  Files          10       10           
  Lines         360      360           
=======================================
  Hits          293      293           
  Misses         67       67           

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[DominicOram]

Looks good to me, it wasn't immediately clear to me how _walk_odin_metadata was meant to work so added some extra tests until I understood the edge cases. Hope that's ok