Bug 11171: (follow-up) fix a javascript error

Bug 11171: (follow-up) fix a javascript error

The previous patch adds an error on booksellers.pl:

TypeError: a.aoColumns[c] is undefined

It was caused by the add of the new column. The aoColumns DT parameter
should manage it.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit d5281fd41ec4b2f0c497d75550e2c865d96183d8)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>