Gitui returns zero exit code on error

[acceleratesage]

Describe the bug

When calling gitui in a non-git directory, I get the expected error:

> gitui
invalid path
please run gitui inside of a non-bare git repository

However the exit code is zero:

> echo $?
0

Expected behavior
I'd expect a non-zero exit code e.g. 1.

Context (please complete the following information):
This is on macOs 12.5.1 using gitui installed via nix

> gitui --version
gitui 0.21.0

Additional context
This is a problem when scripting shortcuts to call gitui in a directory as errors get swallowed.