!reference keyword in after_script can't handle anchors

If the !reference keyword is used in after_script it can't handle referenced jobs that contain anchors.

.dummy-anchor: &dummy_anchor
- echo "hello"

.dummy1:
  script:
    - *dummy_anchor
      
dummy2:
  script:
   - !reference [.dummy1, script]
  after_script:
   - !reference [.dummy1, script]

Error: jobs:dummy2:after_script config should be an array containing strings and arrays of strings