Update Query.Tree()

Src/Asp.Net/SqlSugar/Abstract/QueryableProvider/QueryableExecuteSql.cs

@@ -335,12 +335,12 @@ namespace SqlSugar
             var entity = this.Context.EntityMaintenance.GetEntityInfo<T>();
             var pk = GetTreeKey(entity);
             var list = this.ToList();
-            return GetTreeRoot(childListExpression, parentIdExpression, pk, list, rootValue);
+            return GetTreeRoot(childListExpression, parentIdExpression, pk, list, rootValue)??new List<T>();
         }
         public  List<T> ToTree(Expression<Func<T, IEnumerable<object>>> childListExpression, Expression<Func<T, object>> parentIdExpression, object rootValue, object[] childIds)
         {
             var list =  this.ToList();
-            return TreeAndFilterIds(childListExpression, parentIdExpression, rootValue, childIds, ref list);
+            return TreeAndFilterIds(childListExpression, parentIdExpression, rootValue, childIds, ref list) ?? new List<T>();
         }
 
         public virtual DataTable ToDataTable()

Src/Asp.Net/SqlSugar/Abstract/QueryableProvider/QueryableExecuteSqlAsync.cs

@@ -565,14 +565,14 @@ ParameterT parameter)
         public async Task<List<T>> ToTreeAsync(Expression<Func<T, IEnumerable<object>>> childListExpression, Expression<Func<T, object>> parentIdExpression, object rootValue, object[] childIds)
         {
             var list = await this.ToListAsync();
-            return TreeAndFilterIds(childListExpression, parentIdExpression, rootValue, childIds, ref list);
+            return TreeAndFilterIds(childListExpression, parentIdExpression, rootValue, childIds, ref list) ?? new List<T>();
         }
         public async Task<List<T>> ToTreeAsync(Expression<Func<T, IEnumerable<object>>> childListExpression, Expression<Func<T, object>> parentIdExpression, object rootValue)
         {
             var entity = this.Context.EntityMaintenance.GetEntityInfo<T>();
             var pk = GetTreeKey(entity); ;
             var list = await this.ToListAsync();
-            return GetTreeRoot(childListExpression, parentIdExpression, pk, list, rootValue);
+            return GetTreeRoot(childListExpression, parentIdExpression, pk, list, rootValue) ?? new List<T>();
         }
         public async Task<List<T>> ToParentListAsync(Expression<Func<T, object>> parentIdExpression, object primaryKeyValue)
         {