Add house empty/not empty condition in scene

[Pierre-Gilles]

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• If your changes affects code, did your write the tests?
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Description of change

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[codecov]

Codecov Report

Merging #1212 (87d2820) into master (fd9d31e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1212   +/-   ##
=======================================
  Coverage   96.48%   96.49%           
=======================================
  Files         648      650    +2     
  Lines        8284     8306   +22     
=======================================
+ Hits         7993     8015   +22     
  Misses        291      291           

Impacted Files	Coverage Δ
server/utils/constants.js	100.00% <ø> (ø)
server/lib/house/house.getUsersAtHome.js	100.00% <100.00%> (ø)
server/lib/house/house.isEmpty.js	100.00% <100.00%> (ø)
server/lib/house/index.js	100.00% <100.00%> (ø)
server/lib/scene/scene.actions.js	97.56% <100.00%> (+0.12%)	⬆️
server/models/house.js	100.00% <100.00%> (ø)

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