[libgit2-glib] ggit-transfer-progress.c: Fix return annotations

[Igor Gnatenko <ignatenko src gnome org>]

commit 97e0da9dab855f5811fa3a0b3d778fd7bd390173
Author: Brian C. Lane <bcl redhat com>
Date:   Wed Aug 30 18:11:53 2017 -0700

    ggit-transfer-progress.c: Fix return annotations
    
    Add (nullable) as needed.

 libgit2-glib/ggit-transfer-progress.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgit2-glib/ggit-transfer-progress.c b/libgit2-glib/ggit-transfer-progress.c
index 571fe43..500bded 100644
--- a/libgit2-glib/ggit-transfer-progress.c
+++ b/libgit2-glib/ggit-transfer-progress.c
@@ -50,7 +50,7 @@ _ggit_transfer_progress_wrap (const git_transfer_progress *progress)
  *
  * Copies @progress into a newly allocated #GgitTransferProgress.
  *
- * Returns: (transfer full): a newly allocated #GgitTransferProgress.
+ * Returns: (transfer full) (nullable): a newly allocated #GgitTransferProgress or %NULL.
  */
 GgitTransferProgress *
 ggit_transfer_progress_copy (GgitTransferProgress *progress)