Key "priority" not initialized in hook_node_access_records()

The return of workflow_access_node_access_records() does not have the key "priority" (see http://api.drupal.org/api/function/hook_node_access_records/6) even is set to "0".

This is causing an PHP 5.3 notice in node_access_acquire_grants().

Here's a patch to fix this.