Fix messages waiting for empty topic (#60)

kafka-ui-api/src/main/java/com/provectus/kafka/ui/cluster/service/ConsumingService.java

@@ -68,12 +68,13 @@ public class ConsumingService {
 				assignPartitions(consumer);
 				seekOffsets(consumer);
 				int pollsCount = 0;
-				while (!sink.isCancelled() || ++pollsCount > MAX_POLLS_COUNT) {
+				while (!sink.isCancelled() && ++pollsCount < MAX_POLLS_COUNT) {
 					ConsumerRecords<Bytes, Bytes> records = consumer.poll(POLL_TIMEOUT_MS);
 					log.info("{} records polled", records.count());
 					records.iterator()
 							.forEachRemaining(sink::next);
 				}
+				sink.complete();
 			} catch (Exception e) {
 				log.error("Error occurred while consuming records", e);
 				throw new RuntimeException(e);