[LawsScheduler] Add missing constexpr

emper/strategies/laws/LawsScheduler.cpp

@@ -102,7 +102,7 @@ auto LawsScheduler::nextFiber() -> Fiber* {
 
 	poped = queues[victim]->popTop(&fiber);
 	if (poped) {
-		if (emper::STATS) {
+		if constexpr (emper::STATS) {
 			auto flag = static_cast<unsigned int>(LawsStrategy::FiberSource::stolen);
 			fiber->setFlag(flag);
 		}