fix import_path None error

archivebox/archive.py

@@ -73,6 +73,7 @@ def merge_links(archive_path=OUTPUT_DIR, import_path=None, only_new=False):
     num_new_links = len(all_links) - len(existing_links)
     if SHOW_PROGRESS:
         print()
+    if import_path:
         print('    > Adding {} new links to index from {} (parsed as {} format)'.format(
             num_new_links,
             pretty_path(import_path),