private FileChannel channel() throws IOException {
        FileChannel channel = channelOrNull();
        if (channel == null)
            return openChannel();
        else
            return channel;
    }
Do a basic sanity check on this index to detect obvious problems.

@throws CorruptIndexException if any problems are found.
storage/src/main/java/org/apache/kafka/storage/internals/log/TransactionIndex.java