Add missing line

src/winio.c

@@ -3183,6 +3183,7 @@ void draw_scrollbar(void)
 				coveredlines += get_folded_segment_length(line);
 			else
 				++coveredlines;
+			line = get_next_visible_line(line);
 		}
 #else
 		coveredlines = editwinrows;