Skin doesn't change or fallback on default when skin is set to Flamingo (capital F)

To reproduce:

• Go to "Administration" > "Presentation"
• In the Skin field type: Flamingo (with a capital F) and save

Result: UI breaks

Expected: change to Flamingo, or fallback to the default Colibri skin (which is what happens when you fill in a name for a skin that doesn't exist).

Also tested using the following values: Colibri, test (skin didn't exist), no value - blank. The result: skin was changed to default colibri every time, so no problem with these values.

Please see attached.