The judgment in an action cognizable under section 8545 (relating to official liability generally) shall constitute a complete bar to any action by the claimant, by reason of the same subject matter, against the local agency of which the defendant in such action is an employee. The judgment in an action under section 8542 (relating to exceptions to governmental immunity) shall constitute a complete bar to any action by the claimant, by reason of the same subject matter, against the employee whose act gave rise to the claim.