Fix `Panel` rendering when it 2 `Panel`s are used

[zhiburt]

Fix `Panel` rendering when it 2 `Panel`s are used

[zhiburt]

The issue is actually not in maxWidth
But when 2 panes are used with different length

[zhiburt]

#[test]
fn render_row_span_with_different_length() {
    let mut grid = Grid::new(3, 2);
    grid.set_cell_borders(DEFAULT_CELL_STYLE.clone());

    grid.set(
        &Entity::Cell(0, 0),
        Settings::new().text("first row").span(2),
    );
    grid.set(&Entity::Cell(1, 0), Settings::new().text("0"));
    grid.set(&Entity::Cell(1, 1), Settings::new().text("1"));
    grid.set(&Entity::Cell(2, 0), Settings::new().text("a longer second row").span(2));

    let expected = concat!(
        "+-------------------+\n",
        "|first row          |\n",
        "+-------------------+\n",
        "|0        |1        |\n",
        "+---------+---------+\n",
        "|a longer second row|\n",
        "+-------------------+\n",
    );

    println!("{}", grid);

    assert_eq!(expected, grid.to_string());
}

[zhiburt]

closed in 06a4522