When a testing OTO i have this error RECOVERABLE ERROR: Argument 1 passed to Invoice::setCoupon() must be an instance of _coupon, null given, called in /home/infoconc/www/amember/application/default/plugins/misc/oto.php on line 93 and defined in line 498 of file /home/infoconc/www/amember/application/default/models/Invoice.php ==DEBUG== NOTICE: Trying to get property of non-object in line 501 of file /home/infoconc/www/amember/application/default/models/Invoice.php