Allow element with no transcription

Closes #196 (closed)

dan/datasets/extract/__init__.py

@@ -161,4 +161,10 @@ def add_extract_parser(subcommands) -> None:
         help="Do not remove beginning, ending and consecutive spaces in transcriptions.",
     )
 
+    parser.add_argument(
+        "--allow-empty",
+        action="store_true",
+        help="Also extract data from element with no transcription.",
+    )
+
     parser.set_defaults(func=run)