Fix handling of unresolved references in verifier.

The verifier should not treat use of unresolved references as a reason to reject
the entire class. Instead, the verifier treats the instruction as a throw. If
that class is run, the interpreter with extra checks will throw an exception.

Bug: 10457426

Change-Id: I3799da843a7ffb3519bbf6dc13a6276519d9cb95