In order to obligate such municipality or other taxing district on any issue of special assessment warrants, on the ground of negligence, the negligence of such municipality or other taxing district must be established and proved as a matter of fact, and in determining such question, the county auditor making the sale shall not be held to be the agent of the municipality or other taxing district which spread the special assessment so as to charge such municipality or taxing district with responsibility for any failure of such county auditor to perform the county auditor’s statutory duties in connection with such sale.