Fix duplicate STOMP subscription id issue

Issue: SPR-15543

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java

@@ -292,12 +292,15 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 					String cachedDestination = entry.getKey();
 					if (getPathMatcher().match(destination, cachedDestination)) {
 						LinkedMultiValueMap<String, String> subs = entry.getValue();
+						// Subscription id's may also be populated via getSubscriptions()
+						if (!subs.containsKey(sessionId) || !subs.get(sessionId).contains(subsId)) {
 							subs.add(sessionId, subsId);
 							this.accessCache.put(cachedDestination, subs.deepCopy());
 						}
 					}
 				}
 			}
+		}
 
 		public void updateAfterRemovedSubscription(String sessionId, String subsId) {
 			synchronized (this.updateCache) {