QPU Monitor: Topology not found display

When the topology is not available (failing at retrieving connection data) then the butto  shows `[]`, it should read `N/A` or `Not Available` and be disabled for clicking. 

<img width="120" height="172" alt="Image" src="https://github.com/user-attachments/assets/26d94be5-4e5f-4cb8-b4b2-1e69527650fb" />