Missing header row in the monitoring suite interface for some layout trees

Description

During the GE2/1 demonstrator refurbishment, it was noticed that the header row for the OptoHybrid tables in the monitoring suite is missing when the first OptoHybrids do not exist in the layout tree. This issue can possibly appear for any sparse layout tree.

Steps to reproduce

Open the monitoring web interface with a layout tree missing the first OptoHybrid index.