Reproduction steps:
1. Open the attached project "GetBoneTransform.zip"
2. Open the "Scenes/SampleScene" Scene
3. Enter Play Mode
4. Select the "Robot Kyle" GameObject in the Hierarchy
5. Disable its "Animator" component in the Inspector
6. Press R and observe the Console

Expected result: function returns null
Actual result: function does not return null

Reproducible with: 2020.3.14f1, 2021.1.15f1, 2021.2.0b5, 2022.1.0a3
Could not test with: 2018.4.36f1, 2019.4.29f1 (functionality to return null is not implemented)

Note: the function returns null only if the GameObject holding the Animator is disabled