Assume an invalid theme is set in APP_THEME:

app.config['APP_THEME'] = ['invalid']

WebpackThemeBundle will then return None for the active theme bundle:

bundle = WebpackThemeBundle(...) bundle._active_theme_bundle is None

This means that WebpackBundleProject will have to deal with a bundle where the following calls will fail on the project:

bundle.entries
bundle.path
...

It should be investigated what impact this has if say an Invenio module does not specify a theme, and decide on what is the desired behavior.