get_commit_diff on commit with unknown parent (#836)

Author: Stephan Dilly

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Fixed
 - do not allow to ignore .gitignore files ([#825](https://github.com/extrawurst/gitui/issues/825))
+- crash in shallow repo ([#836](https://github.com/extrawurst/gitui/issues/836))
 
 ## [0.16.2] - 2021-07-10
 

asyncgit/src/sync/commit_files.rs

@@ -49,7 +49,9 @@ pub(crate) fn get_commit_diff(
     let commit = repo.find_commit(id.into())?;
     let commit_tree = commit.tree()?;
     let parent = if commit.parent_count() > 0 {
-        Some(repo.find_commit(commit.parent_id(0)?)?.tree()?)
+        repo.find_commit(commit.parent_id(0)?)
+            .ok()
+            .and_then(|c| c.tree().ok())
     } else {
         None
     };