mist crashes if you attempt to enter fullscreen with a no-split file, or no loaded file (which defaults to no-split).
$ cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.14s
Running `target\debug\mist.exe`
Window { timestamp: 18, window_id: 1, win_event: Shown }
Window { timestamp: 25, window_id: 1, win_event: FocusGained }
TextEditing { timestamp: 68, window_id: 1, text: "", start: 0, length: 0 }
Window { timestamp: 462, window_id: 1, win_event: FocusLost }
TextEditing { timestamp: 462, window_id: 1, text: "", start: 0, length: 0 }
Window { timestamp: 3200, window_id: 1, win_event: FocusGained }
Window { timestamp: 3249, window_id: 1, win_event: Exposed }
Window { timestamp: 7074, window_id: 1, win_event: Moved(0, 23) }
Window { timestamp: 7074, window_id: 1, win_event: SizeChanged(1536, 841) }
Window { timestamp: 7074, window_id: 1, win_event: Resized(1536, 841) }
thread 'main' panicked at 'attempt to subtract with overflow', src\app.rs:860:53
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\debug\mist.exe` (exit code: 101)