[gssdp] Check arguments in PktInfoMessage public functions

[Jens Georg <jensgeorg src gnome org>]

commit 3cdbb183ebaaa6ad71477fceb87b2778e498c542
Author: Jens Georg <mail jensge org>
Date:   Fri Jul 25 20:41:36 2014 +0200

    Check arguments in PktInfoMessage public functions
    
    Signed-off-by: Jens Georg <mail jensge org>

 libgssdp/gssdp-pktinfo-message.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/libgssdp/gssdp-pktinfo-message.c b/libgssdp/gssdp-pktinfo-message.c
index 56acd92..ed0fe40 100644
--- a/libgssdp/gssdp-pktinfo-message.c
+++ b/libgssdp/gssdp-pktinfo-message.c
@@ -234,11 +234,15 @@ gssdp_pktinfo_message_get_ifindex (GSSDPPktinfoMessage *message)
 GInetAddress *
 gssdp_pktinfo_message_get_local_addr (GSSDPPktinfoMessage *message)
 {
+        g_return_val_if_fail (GSSDP_IS_PKTINFO_MESSAGE (message), NULL);
+
         return message->priv->iface_addr;
 }
 
 GInetAddress *
 gssdp_pktinfo_message_get_pkt_addr (GSSDPPktinfoMessage *message)
 {
+        g_return_val_if_fail (GSSDP_IS_PKTINFO_MESSAGE (message), NULL);
+
         return message->priv->pkt_addr;
 }