Bug 22941: Do not return 500 if sortfield contain parenthesis

Bug 22941: Do not return 500 if sortfield contain parenthesis

Test plan:
Hit /virtualshelves/shelves.pl?op=view&shelfnumber=1&sortfield=author(

You must not get:
Unmatched ( in regex; marked by <-- HERE in m/^author( <-- HERE $/ at /home/vagrant/kohaclone/virtualshelves/shelves.pl line 236

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit f8db499f4a9c71e7a2ffef0fadaecddb938330d4)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>