Fix empty part-of-day logic

[rejas]

Fixes #3727

[sdetweil]

where is the code change? i see tests but no change to compliments.js

[rejas]

Just a draft because its still work in progress. I want to create some tests first

[rejas]

now its ready @sdetweil

[sdetweil]

let timeOfDay = "";

will be true later, an empty string is not same as null

if (timeOfDay &&