Crash when rendering a block with an empty title with alignment right

[kdheepak]

When rendering a block with a empty title with alignment right, I get a crash. Here's a minimal test:

    #[test]
    fn render_crash() {
        let mut buffer = Buffer::empty(Rect::new(0, 0, 15, 3));
        Block::default()
            .title("")
            // .title_position(crate::widgets::block::Position::Bottom)
            .title_alignment(crate::layout::Alignment::Right)
            .render(buffer.area, &mut buffer);
        assert_buffer_eq!(
            buffer,
            Buffer::with_lines(vec![
                "               ",
                "               ",
                "               ",
            ])
        );
    }

Here's the stacktrace from the test:

running 1 test
thread 'widgets::block::tests::render_crash' panicked at src/buffer/buffer.rs:138:9:
Trying to access position outside the buffer: x=15, y=0, area=Rect { x: 0, y: 0, width: 15, height: 3 }
stack backtrace:
   0: rust_begin_unwind
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/std/src/panicking.rs:645:5
   1: core::panicking::panic_fmt
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/panicking.rs:72:14
   2: ratatui::buffer::buffer::Buffer::index_of
             at ./src/buffer/buffer.rs:138:9
   3: ratatui::buffer::buffer::Buffer::set_stringn
             at ./src/buffer/buffer.rs:216:25
   4: ratatui::buffer::buffer::Buffer::set_line
             at ./src/buffer/buffer.rs:251:23
   5: ratatui::widgets::block::Block::render_right_titles::{{closure}}
             at ./src/widgets/block.rs:697:17
   6: core::iter::traits::iterator::Iterator::for_each::call::{{closure}}
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/traits/iterator.rs:855:29
   7: core::iter::adapters::filter::filter_fold::{{closure}}
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/adapters/filter.rs:40:44
   8: core::iter::traits::double_ended::DoubleEndedIterator::rfold
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/traits/double_ended.rs:307:21
   9: <core::iter::adapters::filter::Filter<I,P> as core::iter::traits::double_ended::DoubleEndedIterator>::rfold
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/adapters/filter.rs:185:9
  10: <core::iter::adapters::rev::Rev<I> as core::iter::traits::iterator::Iterator>::fold
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/adapters/rev.rs:64:9
  11: core::iter::traits::iterator::Iterator::for_each
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/traits/iterator.rs:858:9
  12: ratatui::widgets::block::Block::render_right_titles
             at ./src/widgets/block.rs:683:9
  13: ratatui::widgets::block::Block::render_title_position
             at ./src/widgets/block.rs:708:9
  14: ratatui::widgets::block::Block::render_titles
             at ./src/widgets/block.rs:714:9
  15: <ratatui::widgets::block::Block as ratatui::widgets::WidgetRef>::render_ref
             at ./src/widgets/block.rs:532:9
  16: <ratatui::widgets::block::Block as ratatui::widgets::Widget>::render
             at ./src/widgets/block.rs:522:9
  17: ratatui::widgets::block::tests::render_crash
             at ./src/widgets/block.rs:1351:9
  18: ratatui::widgets::block::tests::render_crash::{{closure}}
             at ./src/widgets/block.rs:1349:22
  19: core::ops::function::FnOnce::call_once
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:250:5
  20: core::ops::function::FnOnce::call_once
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
test widgets::block::tests::render_crash ... FAILED

failures:

failures:
    widgets::block::tests::render_crash

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 1332 filtered out; finished in 0.08s

[joshka]

Rewriting the block implementation is next up on my todo list.