Crashes on window resize

[medwards]

gitt seems to crash on window resizes sometimes, this is a collector issue to get a reproducible test case and collect any other info.

[medwards]

4917623 fixed a case where after deeply scrolling the diff, the window was resized to be longer (causing offset + length out of bounds)

However, just found a different case:

thread 'main' panicked at 'assertion failed: self.revision_window_index.selected().unwrap_or(0) <= length', src/model.rs:270:9