fix: Throw NotFoundException when TopicPartition set is empty

Author: p-eye

api/src/main/java/io/kafbat/ui/service/ReactiveAdminClient.java

@@ -445,7 +445,11 @@ public Mono<Void> deleteConsumerGroupOffsets(String groupId, String topicName) {
           Set<TopicPartition> partitions = table.row(groupId).keySet().stream()
               .filter(tp -> tp.topic().equals(topicName))
               .collect(Collectors.toSet());
-          return toMono(client.deleteConsumerGroupOffsets(groupId, partitions).all());
+          // check if partitions have no committed offsets
+          return partitions.isEmpty()
+              ? Mono.error(new NotFoundException("The topic or partition is unknown"))
+              // call deleteConsumerGroupOffsets
+              : toMono(client.deleteConsumerGroupOffsets(groupId, partitions).all());
         })
         .onErrorResume(GroupIdNotFoundException.class,
             th -> Mono.error(new NotFoundException("The group id does not exist")))