wm_add_window: Fix case of app man returning an error, thanks to Rodrigues Bertrand.
wm_add_window: Fix case of app man returning an error, thanks to Rodrigues Bertrand.

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