Previously, the following sequence of events was possible:

Background thread                   Main thread
------------------------------------------------------------------------
Lock::tryAcquire()
    Run to blockingMessage->post()

                                    BlockingMessage::messageCallback()
                                        Run to abortWait.set (1)

Lock::tryAcquire()
    Exit through return true

Lock::~Lock()
    Destroy memory used for Lock

                                    BlockingMessage::messageCallback()
                                        Execute lockedEvent.signal()
                                        Memory already freed, crash