base-color deleted in generated style-sheet

If you use the default base color (i.e. in Garland #0072b9) in your css and you change the color-scheme, the color-context will be deletet.

Sample:
body { background:#0072b9; }
the new generated css will show
body { background:; }

reason:
in the array $conversion the key 'base' is missing
due to the statement 274 "unset ($converion['base']);"

I skiped this statement and it seems to work fine