Bug 30346: Correctly transfer values when editing rules

Bug 30346: Correctly transfer values when editing rules

To test:
--Create a circulation rule with a value in "Overdue fines cap (amount), or edit an existing rule to add it
-Save the new (or edited) rule.
-Edit the same rule again to change any other field. Note that "Overdue fines cap (amount)" is now blank
-Save your edited rule - "Overdue fines cap (amount)" will save as blank.

Apply patch

--Create a circ rule with a value in Overdue fines cap (amount) and check "Cap fine at replacement price" for that same rule.
-Save the rule
-Try ediding the rule and make sure both of those values now save correctly.
-Add several more rules and try playing with both "Cap fine at replacement price" and "Overdue fines cap (amount)". Make sure everything saves right.

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>