API should return empty string

I am using wakatime for macOS to see my coding time in my menubar. When there is no time yet, hackatime api returns a long string (something along the lines of "Start coding to track your time today". That fills up my menubar for no reason. According to https://github.com/wakatime/macos-wakatime/pull/366 Wakatime would in that case return an empty string instead, and I think Hackatime should too