Fix class cast issue arising after ephemeral read eviction

Patch by Alex Petrov; reviewed by Benedict Elliott Smith for CASSANDRA-20256

Author: ifesdjeen

accord-core/src/main/java/accord/local/cfk/Updating.java

@@ -73,6 +73,7 @@
 import static accord.local.cfk.Utils.removeUnmanaged;
 import static accord.local.cfk.Utils.validateMissing;
 import static accord.primitives.Routable.Domain.Range;
+import static accord.primitives.SaveStatus.Uninitialised;
 import static accord.primitives.Timestamp.Flag.UNSTABLE;
 import static accord.primitives.Txn.Kind.EphemeralRead;
 import static accord.primitives.Txn.Kind.ExclusiveSyncPoint;
@@ -787,6 +788,10 @@ static CommandsForKeyUpdate updateUnmanaged(CommandsForKey cfk, SafeCommand safe
         if (safeCommand.current().hasBeen(Status.Truncated))
             return cfk;
 
+        Command orig = safeCommand.current();
+        if (orig.saveStatus() == Uninitialised && orig.txnId().is(EphemeralRead))
+            return cfk;
+
         Command.Committed command = safeCommand.current().asCommitted();
         TxnId waitingTxnId = command.txnId();
         // used only to decide if an executeAt is included _on the assumption the TxnId is_. For ?[EX] this is all timestamps