Every time the search page updates its results the search bar trims all the whitespaces in the query.
This is mildly annoying when using backspace to modify queries as I end up accidentally deleting an extra letter.
There’s also one other side-effect that I found: occasionally spaces get eaten up when typing too slowly:
Firefox 59.0.2 x64 / Windows 10 Pro
Additional remark: I don’t think it’s necessary for whitespaces to be trimmed in the client-side.