Fix derivation for empty data types

[lsrcz]

This pull request fixes derivation for empty data types. For such instances, usually no contexts are needed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 75.28%. Comparing base (08a0bbd) to head (7feb3d7).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
test/Grisette/Core/TH/DerivationData.hs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #272      +/-   ##
==========================================
+ Coverage   75.27%   75.28%   +0.01%     
==========================================
  Files         209      209              
  Lines       30963    30965       +2     
  Branches     2187     2185       -2     
==========================================
+ Hits        23308    23313       +5     
+ Misses       5468     5467       -1     
+ Partials     2187     2185       -2     

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