[MNG-5729] Fix possible NPE with introduction of mononic clock

Author: gnodet

impl/maven-cli/src/main/java/org/apache/maven/cling/event/ExecutionEventLogger.java

@@ -23,6 +23,8 @@
 import java.time.Duration;
 import java.time.Instant;
 import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.temporal.ChronoUnit;
 import java.util.List;
 import java.util.Objects;
 
@@ -278,7 +280,8 @@ private void logStats(MavenSession session) {
 
         logger.info("Total time:  {}{}", formatDuration(time), wallClock);
 
-        logger.info("Finished at: {}", formatTimestamp(finish.atZone(ZoneId.systemDefault())));
+        ZonedDateTime rounded = finish.truncatedTo(ChronoUnit.SECONDS).atZone(ZoneId.systemDefault());
+        logger.info("Finished at: {}", formatTimestamp(rounded));
     }
 
     @Override

impl/maven-core/src/main/java/org/apache/maven/lifecycle/internal/concurrent/BuildPlanExecutor.java

@@ -927,7 +927,7 @@ protected void stop() {
         }
 
         protected Duration wallTime() {
-            return Duration.between(start, end);
+            return start != null && end != null ? Duration.between(start, end) : Duration.ZERO;
         }
 
         protected Duration execTime() {