Nothing in the provisions of this Part relating to the demolition or purchase of unfit premises prejudices or interferes with the rights or remedies of an owner for breach of any covenant or contract entered into by a lessee in reference to premises in respect of which an order is made by the local housing authority under those provisions.
If an owner is obliged to take possession of premises in order to comply with such an order, the taking possession does not affect his right to avail himself of any such breach which occurred before he so took possession.