TOM UI for submission of FLOYDS spectrum requires non-existant grating

[rachel3834]

Describe the bug
When I use the TOM's default UI to request a spectrum, under 'instrument configurations' it pre-populates a menu of grating options. However, this menu does not include a 'None' option, and the FLOYDS instrument doesn't have any gratings.
As a result, when I try to valid the observation requests, I produce a sequence of errors for each configuration saying "non_field_errors: optical_element of type grating is not available on 2M0-FLOYDS-SCICAM instruments"

To Reproduce
Selecting an example target in my TOM, I navigate to the 'Observe' tab on the target page, and chose the 'Spectra' tab, completing the form given with a standard sequence of lamp flat + arc + science spectrum + arc + lamp flat, set up as a sequence of configurations. I don't think the specific parameters of the observations are relevant to this bug.

Expected behavior
The pulldown menu with the grating list should include a 'None' option, or be grayed out if the user selects an instrument which has no gratings. Advice to the user could also be added underneath this menu button as to its relevance for the selected instrument.

Desktop (please complete the following information):

• OS: Mac OS Ventura 13.5.2
• Browser Chrome