CBIT-532:  don't show zero-length files

Change-Id: I19eb0fb963414f4ae3a7fe60d7c521b1a0f3b959
Reviewed-on: http://review.couchbase.org/37287
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>