Fix filename when using language auto detection

mailservice.py

@@ -76,11 +76,14 @@ def main(end):
                     )
 
                     # filename.language.vtt
-                    filename = (
-                        Path(metadata["filename"])
-                        .with_suffix(".{}.vtt".format(metadata["video_language"]))
-                        .name
-                    )
+                    if metadata["video_language"] == "None":
+                        filename = Path(metadata["filename"]).with_suffix(".vtt").name
+                    else:
+                        filename = (
+                            Path(metadata["filename"])
+                            .with_suffix(".{}.vtt".format(metadata["video_language"]))
+                            .name
+                        )
 
                     with open(Path(job).joinpath("audio.vtt")) as f:
                         msg.add_attachment(f.read(), filename=filename)