Core: Fix layer region flip update with NULL argument when using task manager.
Core: Fix layer region flip update with NULL argument when using task manager.

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