Clang doesn't like empty initializers for maps and sets :(

Hello,
Unluckily I've discovered that clang doesn't like empty initialisers for maps and sets. This PR should fix it.
I'm also having 3 out of 9 tests going in timeout, I'm checking if it's due to some sleep values or something else.
If just removing those lines works as well as using explicit empty constructor, do you not think that it would be better to remove those in the other parts too ?