fix: clean up single group value after unmount closes #3963

[logaretm]

What

Fixes an issue where values of group fields with non-array value like radio inputs are not cleaned up on unmount

closes #3963

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.91%. Comparing base (a4603fa) to head (900573d).
⚠️ Report is 529 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3972   +/-   ##
=======================================
  Coverage   95.91%   95.91%           
=======================================
  Files          68       68           
  Lines        2006     2009    +3     
  Branches      515      517    +2     
=======================================
+ Hits         1924     1927    +3     
  Misses         82       82           

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