panic in array index with MOI

Build 2428.

Perf run
http://perf.jenkins.couchbase.com/job/hades/3963/
http://perf.jenkins.couchbase.com/job/hades/3969/

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0xc98 pc=0x831a01]

goroutine 3059 [running]:
panic(0xf1c220, 0xc8200120d0)
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.6/go/src/runtime/panic.go:464 +0x3e6 fp=0xc829011590 sp=0xc829011510
runtime.panicmem()
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.6/go/src/runtime/panic.go:45 +0x49 fp=0xc8290115b8 sp=0xc829011590
runtime.sigpanic()
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.6/go/src/runtime/sigpanic_unix.go:24 +0x2ba fp=0xc829011608 sp=0xc8290115b8
github.com/couchbase/indexing/secondary/memdb.newInsertCompare.func1(0xc90, 0x7f0b9e6e05c0, 0x7f0c7b691d4000)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/memdb.go:93 +0x41 fp=0xc829011688 sp=0xc829011608
github.com/couchbase/indexing/secondary/memdb/skiplist.compare(0xc823fd58d0, 0xc90, 0x7f0b9e6e05c0, 0xffffffffffffff00)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/skiplist/item.go:16 +0x5a fp=0xc8290116a8 sp=0xc829011688
github.com/couchbase/indexing/secondary/memdb/skiplist.(*Skiplist).findPath(0xc82370cea0, 0x7f0b9e6e05c0, 0xc823fd58d0, 0xc8201a3c80, 0xc823ed76e8, 0x0)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/skiplist/skiplist.go:177 +0x1c5 fp=0xc829011728 sp=0xc8290116a8
github.com/couchbase/indexing/secondary/memdb/skiplist.(*Skiplist).deleteNode(0xc82370cea0, 0x7f0b9e6d89c0, 0xc823fd58d0, 0xc8201a3c80, 0xc823ed76e8, 0xc800000c90)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/skiplist/skiplist.go:295 +0x81 fp=0xc829011768 sp=0xc829011728
github.com/couchbase/indexing/secondary/memdb/skiplist.(*Skiplist).DeleteNode(0xc82370cea0, 0x7f0b9e6d89c0, 0xc823fd58d0, 0xc8201a3c80, 0xc823ed76e8, 0x0)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/skiplist/skiplist.go:289 +0x9f fp=0xc8290117a0 sp=0xc829011768
github.com/couchbase/indexing/secondary/memdb.(*Writer).DeleteNode(0xc823ed7680, 0x7f0b9e6d89c0, 0x0)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/memdb/memdb.go:242 +0xce fp=0xc8290117d8 sp=0xc8290117a0
github.com/couchbase/indexing/secondary/indexer.(*memdbSlice).insertSecArrayIndex(0xc82011d400, 0xcaed786820, 0x99, 0x99, 0xc8581c5f00, 0x13, 0x13, 0x1c, 0x5728a07d)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/indexer/memdb_slice_impl.go:426 +0xddd fp=0xc829011c98 sp=0xc8290117d8
github.com/couchbase/indexing/secondary/indexer.(*memdbSlice).insert(0xc82011d400, 0xcaed786820, 0x99, 0x99, 0xc8581c5f00, 0x13, 0x13, 0x1c, 0x2)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/indexer/memdb_slice_impl.go:336 +0x111 fp=0xc829011cf0 sp=0xc829011c98
github.com/couchbase/indexing/secondary/indexer.(*memdbSlice).handleCommandsWorker(0xc82011d400, 0x1c)
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/indexer/memdb_slice_impl.go:298 +0x32e fp=0xc829011f90 sp=0xc829011cf0
runtime.goexit()
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.6/go/src/runtime/asm_amd64.s:1998 +0x1 fp=0xc829011f98 sp=0xc829011f90
created by github.com/couchbase/indexing/secondary/indexer.NewMemDBSlice
/home/couchbase/jenkins/workspace/watson-unix/goproj/src/github.com/couchbase/indexing/secondary/indexer/memdb_slice_impl.go:214 +0xd20