Empty custom config enables rules disabled by default

[krzema12]

Expected Behavior

When I create an empty custom config file and enable it though detekt { config ... }, it should work as if the custom config wasn't enabled.

Observed Behavior

My Gradle config is as follows:

detekt {
    buildUponDefaultConfig = true
    config = files("$projectDir/detekt-custom-config.yml")
}

and the config file is empty. When I run Detekt, I'm getting

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':backend:detekt'.
> Rule 'AbsentOrWrongFileLicense': License template file not found at `/home/piotr/repos/teams/backend/license.template`.
  Create file license header file or check your running path.

I customized one rule that I needed and it now seems to work correctly.

Steps to Reproduce

See above.

Context

This issue caused confusion as the behavior is counter-intuitive, or if it's somehow by design, it's not documented well enough.

Your Environment

• Version of detekt used: 1.15.0
• Version of Gradle used (if applicable): 6.6.1
• Operating System and version: Ubuntu 20.04
• Link to your project (if it's a public repository): (private repo - easy to reproduce given above description)

[krzema12]

Thank you for the express fix!