Fix conversion from a non-nullable value type to the nullable value type

[StefH]

No description provided.

[codecov]

Codecov Report

Merging #189 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #189      +/-   ##
==========================================
+ Coverage   82.47%   82.52%   +0.04%     
==========================================
  Files          37       37              
  Lines        3647     3657      +10     
  Branches      492      493       +1     
==========================================
+ Hits         3008     3018      +10     
  Misses        501      501              
  Partials      138      138

Impacted Files	Coverage Δ
...ystem.Linq.Dynamic.Core/Parser/ExpressionParser.cs	77.81% <100%> (+0.18%)	⬆️

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