No court shall order the sale of any assets of the receivership until a receiver has reported to the court in writing that he has mailed such notices to such creditors at least five days prior to the filing of such report, except that the court may at any time permit the sale of perishable or seasonable goods when necessary to preserve the estate, or may permit the receiver to conduct the business for which he is a receiver as a going business and to sell in the usual course of such business.