It was broken somewhere between 2f490a3403 and
85ce207f40 leading to panic on watch only node:
2021-07-21T16:21:39.201+0200 INFO received Commit {"validator": 3}
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0xbcc59e]
goroutine 486 [running]:
github.com/nspcc-dev/neo-go/pkg/consensus.(*service).newBlockFromContext(0xc0001629a0, 0xc000308000, 0xc0010fa000, 0x2cb417800)
github.com/nspcc-dev/neo-go/pkg/consensus/consensus.go:664 +0xbe
github.com/nspcc-dev/dbft.(*Context).MakeHeader(...)
github.com/nspcc-dev/dbft@v0.0.0-20210302103605-cc75991b7cfb/context.go:270
github.com/nspcc-dev/dbft.(*DBFT).onCommit(0xc000308000, 0x138c998, 0xc000115110)
github.com/nspcc-dev/dbft@v0.0.0-20210302103605-cc75991b7cfb/dbft.go:487 +0x575
github.com/nspcc-dev/dbft.(*DBFT).OnReceive(0xc000308000, 0x138c998, 0xc000115110)
github.com/nspcc-dev/dbft@v0.0.0-20210302103605-cc75991b7cfb/dbft.go:251 +0xef5
github.com/nspcc-dev/neo-go/pkg/consensus.(*service).eventLoop(0xc0001629a0)
github.com/nspcc-dev/neo-go/pkg/consensus/consensus.go:312 +0x7d6
created by github.com/nspcc-dev/neo-go/pkg/consensus.(*service).Start
github.com/nspcc-dev/neo-go/pkg/consensus/consensus.go:262 +0xdc
In fact, nonce is correctly provided by dbft library (since Legacy), we just
need to use it here.