Stop leaking memory

src/repository.c

@@ -1827,10 +1827,15 @@ int git_repository_is_shallow(git_repository *repo)
 {
 	git_buf path = GIT_BUF_INIT;
 	struct stat st;
+	int error;
 
 	git_buf_joinpath(&path, repo->path_repository, "shallow");
+	error = git_path_lstat(path.ptr, &st);
+	git_buf_free(&path);
 
-	if (git_path_lstat(path.ptr, &st) == GIT_ENOTFOUND)
+	if (error == GIT_ENOTFOUND)
 		return 0;
+	if (error < 0)
+		return -1;
 	return st.st_size == 0 ? 0 : 1;
 }