Under the laws of all states in this country just because the patio door does not lock does not in and of itself give you grounds to terminate your lease with your landlord without recourse. I suggest that you write your landlord a note giving him or her 15 days to remedy the problem since it is a security issue and if not remedied, you will hire a person to fix it and the landlord will be billed for such. Keep a copy of the letter for future use and need.If the due date comes and goes, your option is to have a third party come and make the repairs and bill the property owner.