The filters were added in acymailing 1.5.0. You should either unpublish the acymailing plugin or update acymailing.
The acymailing plugin for hikashop (not the hikashop plugin for acymailing) can be unpublished in the configuration under the tab plugins.
Also, another solution would be to just remove the code
$filterClass = acymailing::get('class.filter');
$filterClass->subid = $sub->subid;
$filterClass->trigger('hikaorder_'.$order->order_status);
form that file since anyway your version of acymailing does not handle triggers.