A policy of liability insurance issued to a local public entity or state agency as a named insured shall not be canceled or renewal of such a policy declined for reasons other than nonpayment of premium unless notice is mailed to the named insured at least 45 days prior to the effective date of nonrenewal or at least 60 days prior to the effective date of cancellation. Such notice need not be sent if a renewal notice stating a premium for an additional period of coverage has been sent the named insured at least 45 days before cancellation or expiration of an existing policy and such premium has not been tendered the insurer before such cancellation or expiration. This section shall not require that notice of cancellation or nonrenewal be given an additional insured added by way of endorsement or certificate of insurance.