Fix: libpe_status: Ignore nvpair with invalid id-ref

Previously, we ignored an invalid id-ref attribute in an nvpair and
tried to get a name and value. Now, we skip an nvpair with an invalid
id-ref.

The schema already disallows nvpairs with invalid id-refs.

This breaks behavioral backward compatibility.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>