LP#1308239 precat holds fulfillment logic repair

In cases where there is no hold on a precat copy, avoid trying to find
"related" holds, in part because it's unnecessary, but also because the
implementation assumes a fleshed $self->volume object, which is not
present during precat checkout.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>