[fix] dex: do not write last chunk if its empty

rust-bins/duniter-dbex/src/export_bc.rs

@@ -101,7 +101,9 @@ pub(crate) fn export_bc<B: Backend>(
                 Ok(())
             })?;
         // Write last chunk
+        if !json_blocks.is_empty() {
             write_chunk(chunk_index, json_blocks, output_dir, pretty)?;
+        }
         progress_bar.set_progress(1.0);
 
         reader_handle