Bug 16356: Fix Error 500 when returning an item which itemtype is not in itemtypes...

Bug 16356: Fix Error 500 when returning an item which itemtype is not in itemtypes table

  Test plan :
    * Find an item with itemtype (itype or bilbioitems.itemtype
      depending on syspref) does not exist in itemtypes table
    * If necessary, change itemtype of one of your item
    * Check out this item
    * Try to check it in, you've got a 500 Error and item is not
      returned

    With the patch
    * Try to check your item in. Item is correctly returned

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>