encoding/gob: error out instead of panicking on nil dereference
Do not panic when we encounter nil interface values which are
invalid values for gob. Previously this wasn't caught yet
we were calling reflect.*.Type() on reflect.Invalid values
thereby causing panic:
`panic: reflect: call of reflect.Value.Type on zero Value.`
which is a panic not enforced by encoding/gob itself.
We can catch this and send back an error to the caller.
Fixes #16204
Change-Id: Ie646796db297759a74a02eee5267713adbe0c3a0
Reviewed-on: https://go-review.googlesource.com/24989 Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Rob Pike <r@golang.org>