Caused by java.lang.NullPointerException

When trying to call "releaseSubscription" method in the WebSocketConnectionManager class app crash on subscriptions (null pointer exception )

crash logs

Caused by java.lang.NullPointerException
Attempt to invoke virtual method 'int java.lang.Object.hashCode()' on a null object reference
java.util.concurrent.ConcurrentHashMap.get (ConcurrentHashMap.java:944)
java.util.concurrent.ConcurrentHashMap.containsKey (ConcurrentHashMap.java:972)
com.amazonaws.mobileconnectors.appsync.WebSocketConnectionManager.releaseSubscription (WebSocketConnectionManager.java:357)
com.amazonaws.mobileconnectors.appsync.AppSyncWebSocketSubscriptionCall.cancel (AppSyncWebSocketSubscriptionCall.java:59)

synchronized void releaseSubscription(String subscriptionId) {
if (!subscriptions.containsKey(subscriptionId)) {
throw new IllegalArgumentException("No existing subscription with the given id.");
}

- AppSync SDK Version: [3.1.4]
- Device: [Pixel 4a , OnePlus 6]
- Android Version: [11 , 10]

Start in WebSocketConnectionManager.releaseSubscription at line 357 and trace the cancellation call from AppSyncWebSocketSubscriptionCall.cancel at line 59. Reproduce cancellation with the reported subscription state, then verify the release path no longer crashes with a null key and preserves the intended missing-subscription behavior.

Written by the indexing model from the issue text.