bench: site-menu doesn't show all site names on mobile

On the mobile version of bench, the site menu has a bug which makes it very hard to use due to site names not displaying. The options are all blank.
The work around is to guess a selection and then select the previous or next since the list is in alphabetical order.

No file or test is named in the report. Start by locating the mobile site-menu implementation in the bench application and reproduce the blank-option behavior on a mobile viewport. Done means every site name is visible and selectable in the mobile menu, with a regression check if the surrounding code provides one.

Written by the indexing model from the issue text.