streamingccl: Fix nil linter check error and stream_ingestion_test error

Previously, the stream ingestion test has no error since no
duplicate event is generated. This PR fixes this and nil linter
check error at the same time.

Release note: None

pkg/ccl/streamingccl/streamclient/random_stream_client.go

@@ -369,9 +369,9 @@ func (m *randomStreamClient) Subscribe(
 
 		rng, _ := randutil.NewPseudoRand()
 
+		var keyValCopy *roachpb.KeyValue
 		for {
 			var event streamingccl.Event
-			var keyValCopy *roachpb.KeyValue
 			if numKVEventsSinceLastResolved == config.kvsPerCheckpoint {
 				// Emit a CheckpointEvent.
 				resolvedTime := timeutil.Now()
@@ -407,7 +407,9 @@ func (m *randomStreamClient) Subscribe(
 			if event.Type() == streamingccl.KVEvent {
 				// Use the originally generated KeyValue copy as the KeyValue inside the event might
 				// get modified by ingestion processor's tenant rekeyer.
-				event = streamingccl.MakeKVEvent(*keyValCopy)
+				// 'keyValCopy' will only be set when it is a KV event. Copying the 'keyValCopy' again
+				// to prevent the event being modified by interceptor again.
+				event = streamingccl.MakeKVEvent(*copyKeyVal(keyValCopy))
 			}
 			func() {
 				m.mu.Lock()