LockSet:tryAcquireOrBackoff use optional<ref_wrapper<Qutex>>

Replace the previous Qutex** raw pointer with a std::optional.

smocore/lockSet.cpp

@@ -44,7 +44,8 @@ void LockSet<OriginalCbFnT>::registerInQutexQueues(
 
 template <class OriginalCbFnT>
 bool LockSet<OriginalCbFnT>::tryAcquireOrBackOff(
-	LockerAndInvokerBase &lockvoker, Qutex **firstFailedQutex
+	LockerAndInvokerBase &lockvoker,
+	std::optional<std::reference_wrapper<Qutex>> &firstFailedQutex
 	)
 {
 	if (!registeredInQutexQueues)
@@ -71,9 +72,7 @@ bool LockSet<OriginalCbFnT>::tryAcquireOrBackOff(
 			lockvoker, nRequiredLocks))
 		{
 			// Set the first failed qutex for debugging
-			if (firstFailedQutex) {
-				*firstFailedQutex = &lockUsageDesc.first.get();
-			}
+			firstFailedQutex = std::ref(lockUsageDesc.first.get());
 			break;
 		}