warning of missing rootDir parameter is logged, but rootDir is set in config

[Akkora]

Describe the bug
A warn log message is sent if the property is set, but not if the property is missing. The handling is reverted.
warn: rootDir property is missing, using cwd.

To Reproduce
Steps to reproduce the behavior:

1. Create a scss.bundle.config.json like:

{
  "bundlerOptions": {
    "rootDir": "my-project/src",
    [...]
  },
  [...]
}

2. Start the SCSS bundler with --watch

scss-bundle -c my-project/src/scss-bundle.config.json --watch

Expected behavior
No warn log message is sent, if rootDir is set in config.

Package version: v0.0.0-canary.ad13f8e
Node version: v13.9.0
OS: Windows 10