[gssdp] net: Fix critical if device does not exist

[Jens Georg <jensgeorg src gnome org>]

commit 5728c90082ff3c8a3a7ae59c5b661ce6ebf287e0
Author: Jens Georg <mail jensge org>
Date:   Mon Apr 13 14:05:03 2020 +0200

    net: Fix critical if device does not exist
    
    Part of #6

 libgssdp/gssdp-net-posix.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/libgssdp/gssdp-net-posix.c b/libgssdp/gssdp-net-posix.c
index 3da6cb9..ca42838 100644
--- a/libgssdp/gssdp-net-posix.c
+++ b/libgssdp/gssdp-net-posix.c
@@ -544,7 +544,9 @@ gssdp_net_get_host_ip (GSSDPNetworkDevice *device)
                 break;
         }
 
-        device->address_family = g_inet_address_get_family (device->host_addr);
+        if (device->host_addr != NULL) {
+                device->address_family = g_inet_address_get_family (device->host_addr);
+        }
 
         g_list_free (up_ifaces);
         freeifaddrs (ifa_list);