Bug 15030 - Certain values in serials' items are lost on next edit

Bug 15030 - Certain values in serials' items are lost on next edit

When editing serials subscription, we can edit them but some values are not pulled from the DB correctly to be put in the edit box.  If not noticed, the value will be overwritten on the next save.

Test:
- Create a subscription
- Edit itemcallnumber (952o?) and make sure to have a different value than the default one.
- Save.
- Edit it again
- The saved value is not there.

This is true for itemcallnumber and a few other fields.

This was caused by calls to ->field($subfield).  This would always fail, of course.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>