[bugfix] FS#13709 - Mpegplayer conflicts with additional fonts in the theme
FONT_UI is a placeholder when it gets assigned it isn't resolved
immediately
when its time to resolve the font it is processed with font_get(int font)
first it sets it to the last slot
and then decrements till it gets a valid font
I think this is intended to allow the largest
chance of getting a loaded font
instead if global_status->font_id has been set use that
similar to how the screen helper does
Change-Id: If97e504466265fafecbe07b7b72adb4808b67e6a