Fix underline interruption with empty cells

Since completely empty cells are not reported by the renderable cells
iterator, the line renderer has incorrectly assumed that these cells did
not cause any change in cell state, leading to underlines spanning empty
cells.

Instead of assuming that the line state is unchanged, the line
calculation now correctly interprets a jump in the renderable cells
column as an interruption of the line.

This fixes #1960.

0 files changed, 0 insertions, 0 deletions