panic when Ctrl-O targets outside of buffer

[sshilovsky]

Summary

Ctrl-O panics if target position is out of buffer bounds

Reproduction Steps

1. open new file
2. create content:

1234567890

3. from normal mode, type sequence: gggl Ctrl+S ghddd Ctrl+O
4. observe panic message

Helix log

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 12, Rope/RopeSlice char length 9', /home/sh/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/ropey-1.5.0/src/slice.rs:349:41
stack backtrace:
   0: rust_begin_unwind
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/panicking.rs:143:14
   2: core::result::unwrap_failed
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/result.rs:1785:5
   3: ropey::slice::RopeSlice::char_to_byte
   4: helix_core::graphemes::nth_prev_grapheme_boundary
   5: helix_core::selection::Range::grapheme_aligned
   6: helix_core::selection::Selection::ensure_invariants
   7: helix_view::document::Document::set_selection
   8: helix_term::commands::jump_backward
   9: helix_term::ui::editor::EditorView::handle_keymap_event::{{closure}}
  10: helix_term::ui::editor::EditorView::handle_keymap_event
  11: <helix_term::ui::editor::EditorView as helix_term::compositor::Component>::handle_event
  12: helix_term::compositor::Compositor::handle_event
  13: helix_term::application::Application::handle_terminal_events
  14: helix_term::application::Application::event_loop_until_idle::{{closure}}
  15: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
  16: std::thread::local::LocalKey<T>::with
  17: tokio::park::thread::CachedParkThread::block_on
  18: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
  19: tokio::runtime::Runtime::block_on
  20: hx::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Platform

Linux

Terminal Emulator

alacritty 0.10.1 ()

Helix Version

helix 22.08.1 (43b31f7)

[the-mikedavis]

Duplicate of #2489