[libsoup] SoupCookie: fix the instrospection annotation for get_expires()

[Claudio Saavedra <csaavedra src gnome org>]

commit 186fd9985fae40fcb7f1d8b6e4a5b5655c2c7028
Author: Claudio Saavedra <csaavedra igalia com>
Date:   Wed Apr 11 11:10:34 2018 +0300

    SoupCookie: fix the instrospection annotation for get_expires()
    
    The value returned can be NULL so reflect that in the introspection
    annotation.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=795135

 libsoup/soup-cookie.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/libsoup/soup-cookie.c b/libsoup/soup-cookie.c
index d97b23f..1d0dde3 100644
--- a/libsoup/soup-cookie.c
+++ b/libsoup/soup-cookie.c
@@ -598,10 +598,11 @@ soup_cookie_set_max_age (SoupCookie *cookie, int max_age)
  * soup_cookie_get_expires:
  * @cookie: a #SoupCookie
  *
- * Gets @cookie's expiration time
+ * Gets @cookie's expiration time.
  *
- * Return value: (transfer none): @cookie's expiration time, which is
- * owned by @cookie and should not be modified or freed.
+ * Return value: (nullable) (transfer none): @cookie's expiration
+ * time, which is owned by @cookie and should not be modified or
+ * freed.
  *
  * Since: 2.32
  **/