~/.bin/working-time.go: Write initial file if none is present

Seems I missed this case somehow, because we definitely need to write
the file should it not be present.  It's weird, but okay.  I guess the
logic changed so it does not work anymore?

.bin/working-time.go

	f, err := os.Open(path)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return Day{Start: time.Now()}
		day := Day{Start: time.Now()}
		if os.IsNotExist(err) {
			writeDay(path, day)
		}
		return day
	}
	defer f.Close()