Bug 31595: Don't process extended attributes if none are inlcuded in the file

Bug 31595: Don't process extended attributes if none are inlcuded in the file

This patch simply adds a check to the import process to only process attrbutes if
they have been found in the data

To test:
1 - Import some patrons without extended attributes
2 - Import patrons including extended attributes
3 - Confirm both work unchanged

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 40cff1a774a3a9deea2effb375b3e7272003444c)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 4e4fac93144c174003d49a9d049a52960f34c6e1)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>