BUG #7730: intarray representation of empty arrays

The following bug has been logged on the website:

Bug reference:      7730
Logged by:          elein
Email address:      elein@varlena.com
PostgreSQL version: 9.2.1
Operating system:   Linux
Description:        =


select NULLIF('{1,2,3}'::integer[] - '{3,2,1}'::integer[], '{}'::integer[]);
This returns an empty array.  It should return NULL. =


Per RhodiumToad: the core code represents '{}' as an array with 0
dimensions, whereas intarray represents it as an array with 1 dimension but
0 elements

intarray should use the same standards as the core code if possible.  I
peered at the code and don't see anything untoward but did not have time to
spend on it.