Supress convertion of zero hours to '12' for intervals when using

Supress convertion of zero hours to '12' for intervals when using
to_char with HH, e.g.

	to_char(interval '0d 0h 12m 44s', 'DD HH24 MI SS');

now returns:

	 00 00 12 44

not:

	 00 12 12 44