更改任务查找方法以提高灵活性

将 `First()` 方法更改为 `FirstOrDefault()`，以便在未找到任务时返回 `null`，从而增强代码在处理无可用任务时的灵活性。

YWGC/FJK/WCS.WorkEngineering/Systems/SrmSystems.cs

@@ -295,7 +295,7 @@ namespace WCS.WorkEngineering.Systems
                     if (!tasks.Any()) throw new KnownException("无可用任务", LogLevelEnum.Mid);
 
                     //按条件先后排序获取一条排序后第一条结果1.优先级2.所在楼层与本次优先执行楼层
-                    var task = tasks.OrderByDescending(v => v.Priority).ThenByDescending(v => v.Floor == floor ? 1 : 0).First() ?? throw new KnownException($"{obj.Entity.Code}未找到入库任务", LogLevelEnum.High);
+                    var task = tasks.OrderByDescending(v => v.Priority).ThenByDescending(v => v.Floor == floor ? 1 : 0).FirstOrDefault() ?? throw new KnownException($"{obj.Entity.Code}未找到入库任务", LogLevelEnum.High);
 
                     //获取任务所有设备
                     station = arrIn.First(v => (v.Data.TaskNumber == task.ID) || (v.Data2.TaskNumber == task.ID));