Delete this
if exists (select * from dbo.mydatabase where id = OBJECT_ID(N'[dbo]. [new_table]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[new_table]
GO
Add this
if object_id('dbo.new_table') is not null
drop table [dbo].[new_table]
GO