app crashes when retrying all subscriptions

**Describe the bug**
After obtaining the connection, the application crashes when trying to use the websocket while it is null. Seems to happen when trying to retry the subscriptions.

**Expected behavior**
Should subscribe successfully or try subscribing later

**Screenshots**

**Environment(please complete the following information):**
- AppSync SDK Version: 3.3.2

**Device Information (please complete the following information):**
- Android Version: 10

Start with the subscription retry path described in the report and reproduce the websocket-null crash on Android 10 with AppSync SDK 3.3.2. Trace the retry-all-subscriptions flow and verify the expected behavior: subscriptions succeed when possible or retry later when the websocket is unavailable.

Written by the indexing model from the issue text.