Error 404 on a workflow when rights inheritance is blocked

To reproduce :
1. Create a WS,
2. Give rights to a user A on the WS,
3. Create a document in the WS,
4. Block rights inheritance,
5. Start a WF on the document and add user A on the WF,
6. Approve the document.
7. With user A, go on the dashboard.
-> The document is displayed in the tasks.
8. Click on it.
-> Error 404.