Fix CellForeground and CellBackground cursor colors
Fix CellForeground and CellBackground cursor colors

This commit fixes regression introduced in
bedf5f3004e8f33011925ca471be02ead96f4581, when setting
certain CellForeground/CellBackground combinations stoppped working.
jwilm/alacritty,jwilm/alacritty,jwilm/alacritty,alacritty/alacritty,jwilm/alacritty,alacritty/alacritty