A release by the injured person of one joint tort-feasor does not relieve him from liability to make contribution to another tort-feasor, unless the release is given before the right of the other tort-feasor to secure a money judgment for contribution has accrued and provides for a reduction to the extent of the pro rata share of the released tort-feasor of the injured person's damages recoverable against all the other tort-feasors.
42 Pa.C.S. § 8327