cmd/go: don't construct module version info if there are import errors
A precondition of modload.PackageBuildInfo is that its path and deps
arguments correspond to paths that have been loaded successfully with
modload.ImportPaths or one of the Load functions. load.Package.load
should not call PackageBuildInfo if there were any errors resolving
imports.
Fixes #34393
Change-Id: I107514f1c535885330ff266c85d3981b71b31c2d
Reviewed-on: https://go-review.googlesource.com/c/go/+/196520
Run-TryBot: Jay Conrod <jayconrod@google.com> Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>