rule.parent may be undefined

[a-x-]

fixes #121

[a-x-]

AFTER MERGE

should update whole list of plugins:

<prj>/.babelrc
\/
babel-plugin-css-modules-transform
\/                            ||
css-modules-require-hook      ||
\/                            \/
postcss-modules-local-by-default aka postcss-icss-selectors
\/
bug: rule.parent is undefined

https://github.com/a-x-/css-modules-require-hook
https://github.com/a-x-/babel-plugin-css-modules-transform