list-objects.c: handle unexpected non-tree entries

Apply similar treatment as the previous commit for non-tree entries,
too.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t6102-rev-list-unexpected-objects.sh b/t/t6102-rev-list-unexpected-objects.sh
index 1377c60..e3ec195 100755
--- a/t/t6102-rev-list-unexpected-objects.sh
+++ b/t/t6102-rev-list-unexpected-objects.sh
@@ -34,8 +34,9 @@
 	test_must_fail git rev-list --objects $broken_tree
 '
 
-test_expect_failure 'traverse unexpected non-tree entry (seen)' '
-	test_must_fail git rev-list --objects $blob $broken_tree
+test_expect_success 'traverse unexpected non-tree entry (seen)' '
+	test_must_fail git rev-list --objects $blob $broken_tree >output 2>&1 &&
+	test_i18ngrep "is not a tree" output
 '
 
 test_expect_success 'setup unexpected non-commit parent' '