For the purposes of automobile liability insurance, covering liability arising out of the ownership, maintenance, or use of any motor vehicle registered or principally garaged in this state, unless the context otherwise requires, “uninsured motor vehicle” shall be deemed to include, subject to the terms and conditions of the coverage, an insured motor vehicle when the liability insurer thereof is unable to make payment with respect to the legal liability of its insured with the limits specified therein because of insolvency.