Add null checks within pingListeners

gselzer · ctrueden · commit 2c534d5be8eb · 2022-04-13T11:46:52.000-05:00
diff --git a/scijava/scijava-ops-engine/src/main/java/org/scijava/ops/engine/progress/Progress.java b/scijava/scijava-ops-engine/src/main/java/org/scijava/ops/engine/progress/Progress.java
@@ -2,6 +2,7 @@
 
 import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -44,6 +45,7 @@ private static synchronized void createListenerList(Object progressible) {
 	public static void popExecution() {
 		ProgressibleObject completed = progressibleStack.get().pop();
 		completed.task().complete();
+		pingListeners();
 	}
 
 	public static void pushExecution(Object progressible) {
@@ -60,7 +62,8 @@ public static void pushExecution(Object progressible) {
 
 	private static void pingListeners() {
 		ProgressibleObject o = progressibleStack.get().peek();
-		List<ProgressListener> list = progressibleListeners.get(o.object());
+		if (o == null) return;
+		List<ProgressListener> list = progressibleListeners.getOrDefault(o.object(), Collections.emptyList());
 		synchronized (list) {
 			list.forEach(l -> l.updateProgress(o.task()));
 		}
