Fixed #13107: Adjusted decimal_places validation to accept 0 as a valid value....

Fixed #13107: Adjusted decimal_places validation to accept 0 as a valid value. Thanks to loewis for report.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@12774 bcc190cf-cafb-0310-a4f2-bffc1f526a37