JIRA: https://jira.spring.io/browse/INT-4075
Fixes GH-1854 (https://github.com/spring-projects/spring-integration/issues/1854)
The `catch` block just swallows an Exception with the logger and leaves `stompSessionListenableFuture` as `null`.
The next `stompSessionListenableFuture` usage over two code lines bellow ends up with `NPE`.
* Add reconnect logic into that `catch` block and just return from there, since we don't have anything to go ahead.
* Add `if (e != null) {` around `log.error` in the `scheduleReconnect`
* Add `if...else` around `this.stompClient.getTaskScheduler()` and `log.info()` to notify end-user that there won't be reconnection if there is no `taskScheduler`
* Add `StompSessionManagerTests` mock tests to verify solution
**Cherry-pick to 4.2.x**
bce851576e