Update dm

Src/Asp.Net/DmTest/Demo/Demo2_Updateable.cs

@@ -43,6 +43,7 @@ namespace OrmTest
             //update all columns by primary key
             var result = db.Updateable(updateObj).ExecuteCommand();//update single
             var result2 = db.Updateable(updateObjs).ExecuteCommand();//update List<Class>
+            var result21 = db.Updateable(new List<Order>() { }).ExecuteCommand();
 
             //Ignore  Name and Price
             var result3 = db.Updateable(updateObj).IgnoreColumns(it => new { it.CreateTime, it.Price }).ExecuteCommand();

Src/Asp.Net/SqlSugar/Realization/Dm/SqlBuilder/DmUpdateBuilder.cs

@@ -28,7 +28,7 @@ namespace SqlSugar
                 return string.Format("{0} {1} WHERE {2};", updateTable, setValues, string.Join("AND", whereList));
             }).ToArray()));
             var result= sb.ToString();
-            if (result == "\r\n") 
+            if (groupList.Count==0) 
             {
                 return null;
             }