Duplicate pipelines on merge request if set rule for commit changes without merge request

Summary

We need filtered jobs for some files changes and we set 3 rules:

• If it merge request with changes
• If it commit without merge request with same changes
• If it commit in master branch for all

But is cause two pipelines - detached and for commit.

Steps to reproduce

This .gitlab-ci.yml config reproduce problem

stages:
  - test

workflow:
  rules:
    - if: $CI_MERGE_REQUEST_ID
    - if: $CI_COMMIT_BRANCH == "master"
    - if: $CI_MERGE_REQUEST_ID == null
    
rules-test:
  stage: test
  rules:
    - if: $CI_MERGE_REQUEST_IID
      changes:
        - .gitlab-ci.yml
    - if: $CI_COMMIT_BRANCH == "master"
    - if: $CI_MERGE_REQUEST_IID == null
      changes:
        - .gitlab-ci.yml
  script:
    - echo 'Check rules'

Example Project

Quron/duplicate-pipeline-with-rules!1

What is the current bug behavior?

This condition is cause 2 pipelines on merge request

 rules:
    - if: $CI_MERGE_REQUEST_IID
    - if: $CI_MERGE_REQUEST_IID == null

1 - https://gitlab.com/Quron/duplicate-pipeline-with-rules/pipelines/117560934

2 - https://gitlab.com/Quron/duplicate-pipeline-with-rules/pipelines/117560932

What is the expected correct behavior?

If rule check for mr is true, leave only detached pipeline

Output of checks

This bug happens on GitLab.com