libs/vkd3d: Assert that queue is valid in vkd3d_queue_acquire().

Signed-off-by: Józef Kucia <jkucia@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>

libs/vkd3d/command.c

@@ -66,6 +66,7 @@ static VkQueue vkd3d_queue_acquire(struct vkd3d_queue *queue)
         return VK_NULL_HANDLE;
     }
 
+    assert(queue->vk_queue);
     return queue->vk_queue;
 }