Fix failure for dishwasher without "OpzProg"

[dzamlo]

See https://community.home-assistant.io/t/dishwasher-candy-simply-fi-cdi-6015-wifi/136543/152 for an exemple of somebody with a dishwasher without the "OpzProg" property

[codecov]

Codecov Report

Merging #27 (f376529) into main (60d3049) will increase coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   88.64%   88.82%   +0.18%     
==========================================
  Files           6        6              
  Lines         555      555              
==========================================
+ Hits          492      493       +1     
+ Misses         63       62       -1     

Impacted Files	Coverage Δ
custom_components/candy/client/model.py	80.47% <100.00%> (+0.59%)	⬆️

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[ofalvai]

Thanks for catching this @dzamlo!