eth/tracers: fix unigram tracer's return value

[s1na]

Fixes #22208. The issue is that the tracer doesn't return a value (i.e. in js-land it returns undefined) if a tx was transfer-only, and one transfer tx in the block was enough to make the whole call fail.

I'm not sure what's wrong with my go-bindata. I run go generate eth/tracers/internal/tracers/tracers.go but it changes the generated code by a bit.

[holiman]

LGTM, except from the bindata. We use https://github.com/kevinburke/go-bindata, afaik

[holiman]

Yes, if you do make devtools, it downloads

go: downloading github.com/kevinburke/go-bindata v3.22.0+incompatible

So that's what's used on e.g. travis-builds.

[s1na]

Ah hadn't seen make devtools. I'm facing an error though, will have to investigate:

accounts/abi/bind/backend.go:24:2: import "github.com/ethereum/go-ethereum" is a program, not an importable package
make: *** [Makefile:53: devtools] Error 1

But for now I manually got the other go-bindata version and updated the PR.

[holiman]

LGTM