Bug 12288: fix search errors with AggressiveMatchOnISBN turned on

Bug 12288: fix search errors with AggressiveMatchOnISBN turned on

This patch fixes a problem where search errors like this in the logs when
running a stage import with the AggressiveMatchOnISBN syspref turned on:

search failed (isbn,phr=978-0-7517-9745-9 or isbn,phr=0-7517-9745-6 or
isbn,phr=978-0-7517-9745-9 or isbn,phr=0751797456 or
isbn,phr=9780751797459 or isbn,phr=978-0-7517-9759-6 or
isbn,phr=0-7517-9759-6 or isbn,phr=978-0-7517-9759-6 or
isbn,phr=0751797596 or isbn,phr=9780751797596 or isbn,phr= or
isbn,phr= or isbn,phr= or isbn,phr= or isbn,phr=) CCL parsing
error (10014) Search word expected ZOOM at
/usr/share/koha/lib/C4/Matcher.pm line 688.

This is most easily seen when running the script from command line
/misc/stage_file.pl.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>