In all leases containing a covenant, condition, or agreement against assigning, underletting, or parting with the possession, or disposing of the land or property leased without licence or consent, such covenant, condition, or agreement shall, unless the lease contains an express provision to the contrary, be deemed to be subject to a proviso to the effect that no fine or sum of money in the nature of a fine shall be payable for or in respect of such licence or consent; but this proviso does not preclude the right to require the payment of a reasonable sum in respect of any legal or other expense incurred in relation to such licence or consent.