Fix NPE produced by a call from InternalTableImpl#enlistWithRetry()

I'm doing the following:

1. Start a cluster of 3 nodes
2. Create a table with 3 replicas and 1 partition
3. Stop one node
4. Make a snapshot on the leader of the partition (twice in a row) - I'm not sure this step is required to reproduce the issue
5. Start the stopped node

Then in this code
private <R> CompletableFuture<R> enlistWithRetry(
InternalTransaction tx,
int partId,
BiFunction<TablePartitionId, Long, ReplicaRequest> requestFunction,
int attempts
) {
CompletableFuture<R> result = new CompletableFuture<>();

enlist(partId, tx).<R>thenCompose(
primaryReplicaAndTerm -> {
try {
return replicaSvc.invoke(
primaryReplicaAndTerm.get1(),
requestFunction.apply((TablePartitionId) tx.commitPartition(), primaryReplicaAndTerm.get2())
);
primaryReplicaAndTerm turns out to contain null as first element, 1 as second element, which causes an NPE further. Probably, clusterNodeResolver returned null.

This does not reproduce often, but I saw this a few times.