[tryout fix] concurrency bug in NamespacedHierarchicalStore#computeIfAbsent(Object, Object, Function) junit-team#5171 junit-team#5209

Signed-off-by: Vincent Potucek <vpotucek@me.com>

Author: Vincent Potucek

junit-platform-engine/src/main/java/org/junit/platform/engine/support/store/NamespacedHierarchicalStore.java

@@ -245,9 +245,9 @@ public <K, V> Object computeIfAbsent(N namespace, K key, Function<? super K, ? e
 		var result = StoredValue.evaluateIfNotNull(storedValue);
 		if (result == null) {
 			var value = storedValues.compute(compositeKey, (__, currentValue) ->
-					currentValue != null && !currentValue.equals(storedValue)
-					? currentValue
-					: storeNewValue(key, defaultCreator));
+					currentValue == null || currentValue.equals(storedValue)
+							? storeNewValue(key, defaultCreator)
+							: currentValue);
 			try {
 				return requireNonNull(value.evaluate());
 			}