Fix bug rendering inverted cells
Fix bug rendering inverted cells

Cells with no content that had the cell::INVERSE flag were not being
rendered. This was noticeable in `man` where the bar at the bottom would
have gaps in it.

jwilm/alacritty,alacritty/alacritty,dannydulai/alacritty,alacritty/alacritty,jwilm/alacritty,jwilm/alacritty,dannydulai/alacritty,jwilm/alacritty