fixed a bug

app.py

@@ -45,6 +45,7 @@ def download_video(url,format_id):
             save_location = meta['id'] + '.' + meta['ext']
         except youtube_dl.DownloadError as error:
             print(f'error with download_video function: {error}')
+        return(save_location)
 
 def process_video_parallel(video, skip_frames, dest_path, num_processes, process_number):
     cap = cv2.VideoCapture(video)