[layers] Fixed unlocking of destroyed skirmish in context destructor.
[layers] Fixed unlocking of destroyed skirmish in context destructor.

[merged from release_1_2_x]

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