Dropdown menus dont work with only one entry

[Santonia27]

Preliminary Checklist

• I have searched the existing issues list for similar reports and found none. If you did find a similar issue, please add a comment to the existing issue instead of opening a new one.
• I have verified that the issue exists in the latest version of DelftDashboard and its dependencies. Please update to the latest version and check if the issue still exists.

Severity Level

Medium

Steps to reproduce

Any dropdown manu with only one option does not work. There need to be 2 options for the gui to be able to select the right index.

Current behaviour

Any dropdown manu with only one option does not work. There need to be 2 options for the gui to be able to select the right index.

Desired behaviour

that either it is no issue to have only one entry or to add a default entry saying "Select data", so that there are always 2 entries

Additional context

No response