Nil pointer error in yfast trie

[shabbyrobe]

Here's a minimal reproducing example using Go 1.9 on macOS Sierra. I couldn't break it down any further. It will fail pretty much every time, but at a different loop iteration. I tried to simplify the example but this was the simplest that would reliably reproduce the problem.

type Entry uint64

func (s Entry) Key() uint64 { return uint64(s) }

func main() {
	y := yfast.New(uint64(1))

	i := 0
	defer func() {
		err := recover()
		fmt.Println(i)
		panic(err)
	}()
	for ; i < 10000; i++ {
		e1 := Entry(time.Now().UnixNano())
		y.Insert(e1)

		e2 := Entry(time.Now().Add(20 * time.Millisecond).UnixNano())
		y.Insert(e2)

		e3 := Entry(time.Now().Add(10 * time.Millisecond).UnixNano())
		y.Insert(e3)

		y.Delete(e3.Key())
	}
}