[io/Stats] do not try to print the globalIo stats if there are none

emper/io/Stats.cpp

@@ -119,7 +119,9 @@ auto operator<<(std::ostream& os, const Stats& s) -> std::ostream& {
 
 void Stats::printStats(IoContext* globalIoContext,
 											 const std::vector<IoContext*>& workerIoContexts) {
-	std::cout << globalIoContext->getStats() << std::endl;
+	if (globalIoContext) {
+		std::cout << globalIoContext->getStats() << std::endl;
+	}
 
 	// Use a stats object to calculate the averages
 	Stats avgs;