TypeError: %d format: a number is required, not NoneType

Steps to reproduce:

1. open a v1 alg in the editor: livdet_baseline.tar.xz
2. answer yes to its migration to v2
3. save it:

Traceback (most recent call last):
  File "/home/amir/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/assetwidget.py", line 520, in saveJson
    is_valid, errors = self.current_asset.is_valid()
  File "/home/amir/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/backend/asset.py", line 269, in is_valid
    _, error_list = self.type.validate(self.declaration_path)
  File "/home/amir/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/backend/asset.py", line 112, in validate
    return validate(self.name.lower(), data)
  File "/home/amir/miniconda/envs/iris/lib/python3.7/site-packages/beat/core/schema/__init__.py", line 176, in validate
    validator = load_schema(schema_name, version)
  File "/home/amir/miniconda/envs/iris/lib/python3.7/site-packages/beat/core/schema/__init__.py", line 93, in load_schema
    __name__, os.path.join(schema_name, "%d.json" % version)
TypeError: %d format: a number is required, not NoneType