Work with cbz files with subdirectories

backend.py

@@ -259,7 +259,9 @@ class CalibreDB(BaseDB):
         path = self.get_volume_filepath(volume_id)
         with ZipFile(path, 'r') as volume:
             try:
-                zip_info = volume.filelist[page_number - 1]
+                # filter sub directories
+                filelist = [file for file in volume.filelist if not file.is_dir()]
+                zip_info = filelist[page_number - 1]
             except IndexError:
                 raise exceptions.NotFound()
                 return None