Bug 19539: Fix column index shift in cirulation rules

Bug 19539: Fix column index shift in cirulation rules

This patch fixes an index shift introduced by bug 18857 when it introduced
a new column.

To test:
- On the Circulation and fine rules page
- Empty the value of 'Current on-site checkouts allowed' and save
- Notice 'Unlimited' shows on the saved rule.
- Click edit
=> FAIL: the 'Unlimited' string displays instead of the empty string on the editing row.
- Apply this patch
- Re-open the circ rules page
- Click edit
=> SUCCESS: An empty string fills the 'Unlimited' fields
- Sign off :-D

Signed-off-by: David Bourgault <david.bourgault@inlibro.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>