go-fuzz: don't drop data when Read also returns an error
go-fuzz: don't drop data when Read also returns an error

The io.Reader contract specifies that Read may
return n > 0 and err != nil, and that in that scenario,
the caller should process those n bytes.

This is rare enough that it probably wasn't causing an actual problem.

Fix it nevertheless; one fewer latent bug.


dvyukov/go-fuzz,dvyukov/go-fuzz