IGNITE-21261 Fix exception 'Unknown topic' is never thrown in KafkaToIgniteMetadataUpdater (#253)

diff --git a/modules/cdc-ext/src/main/java/org/apache/ignite/cdc/kafka/KafkaToIgniteMetadataUpdater.java b/modules/cdc-ext/src/main/java/org/apache/ignite/cdc/kafka/KafkaToIgniteMetadataUpdater.java
index 6135b9d..97b5bfe 100644
--- a/modules/cdc-ext/src/main/java/org/apache/ignite/cdc/kafka/KafkaToIgniteMetadataUpdater.java
+++ b/modules/cdc-ext/src/main/java/org/apache/ignite/cdc/kafka/KafkaToIgniteMetadataUpdater.java
@@ -107,7 +107,7 @@
 
         List<PartitionInfo> topicMeta = cnsmr.partitionsFor(metaTopic, Duration.ofMillis(kafkaReqTimeout));
 
-        if (topicMeta == null)
+        if (F.isEmpty(topicMeta))
             throw new IgniteException("Unknown topic: " + metaTopic);
 
         parts = topicMeta