Keyboard layout indicator in Slick Greeter visually switches to US when pressing modifier keys (Ctrl, Shift, Alt, Super, Caps Lock)

[anti-xeelee]

On the Linux Mint login screen, the keyboard layout selector at the top right shows the currently active layout. I have a physical Spanish (Latin American) keyboard and I manually select "Spanish (Latin American)" from the layout selector. The indicator correctly shows "Latam", until I press any modifier key (Ctrl, Shift, Alt, Super, or Caps Lock). At that moment, the visual indicator changes to "US", even though my keyboard physically continues typing in Latam. Manually re-selecting Latam from the dropdown fixes the indicator until the next modifier key is pressed.

Steps to reproduce

1. On the Linux Mint login screen, use the layout selector (top right corner) and choose "Spanish (Latin American)".
2. Observe that the indicator shows "Latam" (or the corresponding abbreviation).
3. Press only a modifier key: Ctrl, Shift, Alt, Super (Windows key), or Caps Lock.
4. Watch the layout indicator: it visually changes to "US", even though the actual keyboard layout has not changed.
5. Type in the password field and confirm that the keyboard still behaves as Latam (e.g., ñ, accents, and other characters work correctly).

Expected behavior
The layout indicator should not change when pressing modifier keys. It should always display the currently active layout (Latam in this case).

Actual behavior
Pressing Ctrl, Shift, Alt, Super, or Caps Lock causes the layout indicator to jump to "US", while the actual keyboard layout remains Latam.