`on ML <action> duration <duration>` block in the MakeCode project causes console error

[microbit-grace]

Including on ML <action> duration <duration> block in the MakeCode project seems to cause Uncaught TypeError: Cannot read properties of null (reading 'name') in the console. It doesn't seem to have any negative user-facing side effects though.

Repro steps

1. Go to https://createai.microbit.org/
2. Create a new session.
3. Add/import data samples.
4. Train model.
5. Click "Edit in MakeCode"
6. Drag and drop on ML <action> duration <duration> block into the workspace.
7. Navigate back to testing model page.
8. See error described above in console:

Uncaught TypeError: Cannot read properties of null (reading 'name')
    at o (VM1135 pxtembed.js:15:2994516)
    at VM1135 pxtembed.js:15:2995075