Theme variant display bug in theme picker

[James Gryphon]

I've had a curious problem, and don't seem to be able to figure it out on my own, so I thought I'd bring it up here.

I set up Core with three theme variants a while ago, "Classic", "Experimental", and "Castaways". They all run fine, but the theme picker page looks like this:


The default theme is "Classic", but it always shows that ";vrt=Experimental" string, no matter what variant is actually selected, and the pulldown menus are always initially set at "Experimental" (although selecting and using/previewing theme variants still works fine).