It used to be that when the start offset was valid, it was presumed the end was
as well.
This was not true in the case where the start offset was not supplied but could
be inferred (at the very start of the file).
Fixesgolang/go#31797
Change-Id: Ie5a079796fa0f77cef5571a4e5b309c798e1e06b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/174943
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>