场景中无light时会报错

```lua [2024-07-28 22:58:32.32][ERROR]( ant.window|window ) attempt to index a nil value (local 'D') stack traceback: ( service:6 ) F:/ant/ant/pkg/ant.render/shadow/shadow_system.lua:268: in upvalue 'init_light_info' F:/ant/ant/pkg/ant.render/shadow/shadow_system.lua:343: in local 'func' F:/ant/ant/pkg/ant.world/main.lua:379: in upvalue 'update_func' F:/ant/ant/pkg/ant.world/main.lua:404: in field '_pipeline_update' F:/ant/ant/pkg/ant.world/main.lua:588: in method 'pipeline_update' F:/ant/ant/pkg/ant.window/service/window.lua:81: in upvalue 'f' ``` 可否在D为nil时，shadow_sys:update_camera_depend()函数直接return ~