Avoid making reference to packed field.
Avoid making reference to packed field.

Fixes build on Xenial, Trusty, older GCCs.

JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb