[gupnp-av] Avoid warnings when protocolInfo is missing

[Jens Georg <jensgeorg src gnome org>]

commit 163ea5e3d5f5baafa740acbb9007ecbf93860ca6
Author: Sven Neumann <neumann teufel de>
Date:   Mon Nov 17 10:49:03 2014 +0100

    Avoid warnings when protocolInfo is missing
    
    There should not be run-time warnings when the protocolInfo is
    missing in an DIDL-Lite XML fragment.
    
    Signed-off-by: Sven Neumann <neumann teufel de>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=740265

 libgupnp-av/gupnp-didl-lite-object.c   |    3 +++
 libgupnp-av/gupnp-didl-lite-resource.c |    3 ++-
 2 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/libgupnp-av/gupnp-didl-lite-object.c b/libgupnp-av/gupnp-didl-lite-object.c
index 3cd421e..9d669d7 100644
--- a/libgupnp-av/gupnp-didl-lite-object.c
+++ b/libgupnp-av/gupnp-didl-lite-object.c
@@ -835,6 +835,9 @@ is_resource_compatible (GUPnPDIDLLiteResource *resource,
 
                 res_info = gupnp_didl_lite_resource_get_protocol_info
                                                         (resource);
+                if (res_info == NULL)
+                        continue;
+
                 ret = gupnp_protocol_info_is_compatible (info, res_info);
 
                 g_object_unref (info);
diff --git a/libgupnp-av/gupnp-didl-lite-resource.c b/libgupnp-av/gupnp-didl-lite-resource.c
index f524207..eddabfc 100644
--- a/libgupnp-av/gupnp-didl-lite-resource.c
+++ b/libgupnp-av/gupnp-didl-lite-resource.c
@@ -980,7 +980,8 @@ gupnp_didl_lite_resource_get_protocol_info (GUPnPDIDLLiteResource *resource)
         protocol_info = xml_util_get_attribute_content
                                         (resource->priv->xml_node,
                                          "protocolInfo");
-        g_return_val_if_fail (protocol_info != NULL, NULL);
+        if (protocol_info == NULL)
+                return NULL;
 
         error = NULL;
         info = gupnp_protocol_info_new_from_string (protocol_info, &error);