The previous round of loosening the phrasebook checking to allow

playback of some older (pre-1.0) files removed an [implicit] check
against phrasebook dim being set to zero.  Reinstate as an explicit
check.



git-svn-id: https://svn.xiph.org/trunk/Tremor@17542 0101bb08-14d6-0310-b084-bc0e0c8e3800