How to handle errors and exceptions in SQL Server User Defined Functions (UDF)

ALTER FUNCTION [dbo].[udfSEmailID](@EmpID int)

RETURNS varchar(25)
AS
BEGIN

	Declare @Email varchar(25)  
	select @Email = Employee.EmpEmail from Employee where Employee.Empid=@EmpID
	return @Email


End 

This is User define Scalar function, Can anybody plz help me how to handle error or exception while using above function using SqlServer 2008R2. Thanks