Allow kern_x or kern_y to be NULL.
Allow kern_x or kern_y to be NULL.

deniskropp/DirectFB,djbclark/directfb-core-DirectFB,djbclark/directfb-core-DirectFB,DirectFB/directfb,kevleyski/DirectFB-1,Distrotech/DirectFB,DirectFB/directfb,dfbdok/DirectFB1,deniskropp/DirectFB,jcdubois/DirectFB,lancebaiyouview/DirectFB,sklnet/DirectFB,kevleyski/directfb,kaostao/directfb,kevleyski/directfb,kevleyski/DirectFB-1,jcdubois/DirectFB,jcdubois/DirectFB,djbclark/directfb-core-DirectFB,sklnet/DirectFB,lancebaiyouview/DirectFB,mtsekm/test,mtsekm/test,Distrotech/DirectFB,dfbdok/DirectFB1,kevleyski/DirectFB-1,mtsekm/test,kevleyski/directfb,kaostao/directfb,DirectFB/directfb,lancebaiyouview/DirectFB,dfbdok/DirectFB1,deniskropp/DirectFB,deniskropp/DirectFB,kevleyski/DirectFB-1,kevleyski/directfb,sklnet/DirectFB,sklnet/DirectFB,lancebaiyouview/DirectFB,djbclark/directfb-core-DirectFB,kaostao/directfb,Distrotech/DirectFB