Better check for exceptional floating point values

[awvwgk]

• also trap positive infinity when determining CN weights

Closes #127

[codecov]

Codecov Report

Merging #128 (cb09e48) into main (e027695) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #128      +/-   ##
==========================================
+ Coverage   59.16%   59.20%   +0.04%     
==========================================
  Files          40       40              
  Lines        2946     2949       +3     
  Branches      995      995              
==========================================
+ Hits         1743     1746       +3     
  Misses        642      642              
  Partials      561      561              

Impacted Files	Coverage Δ
src/dftd4/model.f90	79.52% <100.00%> (+0.49%)	⬆️

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[manishkothakonda]

Hi, I want to check back if there is any update on the problem discovered: I am still getting NaN in the OSZICAR compiled with the updated lines of code.