Fix #83, Return nothing if no new version is available

[codedge]

Fix #83

[codecov]

Codecov Report

Merging #89 into master will increase coverage by 0.09%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master      #89      +/-   ##
============================================
+ Coverage     45.86%   45.96%   +0.09%     
  Complexity      159      159              
============================================
  Files            19       19              
  Lines           484      483       -1     
============================================
  Hits            222      222              
+ Misses          262      261       -1     

Flag	Coverage Δ	Complexity Δ
#unittests	45.96% <0.00%> (+0.09%)	159.00 <0.00> (ø)	⬆️

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