fix: out of bounds when rhs line numbers does not match

This is caused by the same problem as before, but the disagreement
seems to be with the Tree itself and happens inside
`syntax::change_positions`, there may be another way to work around
this by removing the correct entry from `rhs_positions` when
the conditions are met.

src/display/side_by_side.rs

@@ -515,14 +515,16 @@ pub(crate) fn print(
                     None => vec![" ".repeat(source_dims.content_width)],
                 };
                 let rhs_line = match rhs_line_num {
-                    Some(rhs_line_num) => split_and_apply(
-                        rhs_lines[rhs_line_num.as_usize()],
-                        source_dims.content_width,
-                        display_options.tab_width,
-                        rhs_highlights.get(rhs_line_num).unwrap_or(&vec![]),
-                        Side::Right,
-                    ),
-                    None => vec!["".into()],
+                    Some(rhs_line_num) if rhs_line_num.as_usize() < rhs_lines.len() => {
+                        split_and_apply(
+                            rhs_lines[rhs_line_num.as_usize()],
+                            source_dims.content_width,
+                            display_options.tab_width,
+                            rhs_highlights.get(rhs_line_num).unwrap_or(&vec![]),
+                            Side::Right,
+                        )
+                    }
+                    _ => vec!["".into()],
                 };
 
                 for (i, (lhs_line, rhs_line)) in zip_pad_shorter(&lhs_line, &rhs_line)