bug 2345 - don't crash when some binary clients send in empty keys
bug 2345 - don't crash when some binary clients send in empty keys

One client that does this is dbmaint, so you can test this fix by
pointing dbmaint against moxi, and moxi doesn't crash anymore...

  ./ep-engine/management/dbmaint --vacuum --port=11211

Change-Id: Ie1908333cb16d3b7a2f33c85ce5e34694db39de9
Reviewed-on: http://review.northscale.com/2427
Reviewed-by: Matt Ingenthron <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@northscale.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

membase/moxi,couchbase/moxi,zbase/moxi,membase/moxi,membase/moxi,zbase/moxi,membase/moxi,steveyen/moxi,couchbase/moxi,couchbase/moxi,zbase/moxi,steveyen/moxi,couchbase/moxi,membase/moxi,couchbase/moxi,steveyen/moxi,steveyen/moxi,membase/moxi,couchbase/moxi,zbase/moxi,steveyen/moxi,zbase/moxi