[FIX] Fixed return type in DataSet.call_button controller.
[FIX] Fixed return type in DataSet.call_button controller.

havt/openerp-web,havt/openerp-web,akretion/openerp-web,havt/openerp-web,akretion/openerp-web,havt/openerp-web,akretion/openerp-web,havt/openerp-web