Particular data sequence causes inconsistency & panic in llrb

[peterwald]

I encountered a crash in a data processing app that makes use of GoLLRB.

panic: runtime error: invalid memory address or nil pointer dereference
at llrb/llrb.go:423 (moveRedLeft)

I found a particular sequence of data that causes the tree to become inconsistent and crash. I've attached a simple test program that reproduces the error.

Download the code file llrbcrash.go and run with:

go get github.com/petar/GoLLRB
go run llrbcrash.go