Core: Fix crash when dfb_wm_update_cursor() is called with 'no-cursor' option.
Core: Fix crash when dfb_wm_update_cursor() is called with 'no-cursor' option.

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