Bug 20592: Return early in ModItem if nothing to update

Bug 20592: Return early in ModItem if nothing to update

Two lines of code and move them earlier.
Add a check to make sure there are changes.

Followed the test plan, both the _BEFORE_ and after do as described.

Signed-off-by: Cori Lynn Arnold <carnold@dgiinc.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 1f0064bbddb9d00529d5eac1c096e669732eb551)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 75d6195c0ef36c4da244c4e2e2341696c94642c1)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>