When writter is nil, we should not ingest events

[atlas-comstock]

// WriteBlock writes a one or multiple blocks to the underlying writer.
func (s *Flusher) WriteBlock(blocks []block.Block, schema typeof.Schema) error {
	if s.writer == nil || len(blocks) == 0 {
		return nil
	}

	// Merge the blocks based on the specified merging function
	// buffer, err := s.merge(blocks, schema)
	// if err != nil {
	//     return err
	// }

	// Generate the file name and write the data to the underlying writer
	return s.writer.Write(s.generateFileName(blocks[0]), blocks)
}

In Flusher, we should return an error when the writer is nil, otherwise, the badgerDB data will be deleted without writing to any writter.
It would be better to keep them in badgerDB

[tardunge]

How about having a Writer scoped Flusher?