If the theme's name was changed, resetting the default theme did
nothing from a user perspective.
Internally it would add the Default theme to the end of the list where
it was ignored, then the default theme overwrote the data including the
next/prev links causing the ListBase to be invalid.
Resolve by ensuring the default theme is always first and use the
MEMCPY_STRUCT_AFTER macro to prevent links being overwritten.
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