[libgit2-glib] Protected against empty signature

[Jesse van den Kieboom <jessevdk src gnome org>]

commit 6d11e4247334a1fb7d6b207df661598a8435b9e4
Author: Jesse van den Kieboom <jkieboom esri com>
Date:   Wed Dec 30 17:42:37 2015 +0100

    Protected against empty signature
    
    Bug https://bugzilla.gnome.org/show_bug.cgi?id=756454.

 libgit2-glib/ggit-tag.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/libgit2-glib/ggit-tag.c b/libgit2-glib/ggit-tag.c
index bde9faa..a226386 100644
--- a/libgit2-glib/ggit-tag.c
+++ b/libgit2-glib/ggit-tag.c
@@ -164,6 +164,11 @@ ggit_tag_get_tagger (GgitTag *tag)
        t = _ggit_native_get (tag);
        signature = git_tag_tagger (t);
 
+       if (signature == NULL)
+       {
+               return NULL;
+       }
+
        return _ggit_signature_wrap ((git_signature *)signature, NULL, FALSE);
 }