Add error func to node deserialization

tests/rendernode.c

@@ -13,6 +13,19 @@ static GOptionEntry options[] = {
   { NULL }
 };
 
+static void
+deserialize_error_func (const GtkCssSection *section,
+                        const GError        *error,
+                        gpointer             user_data)
+{
+  char *section_str = gtk_css_section_to_string (section);
+
+  g_warning ("Error at %s: %s", section_str, error->message);
+
+  free (section_str);
+}
+
+
 int
 main(int argc, char **argv)
 {
@@ -66,7 +79,7 @@ main(int argc, char **argv)
     }
 
   start = g_get_monotonic_time ();
-  node = gsk_render_node_deserialize (bytes, &error);
+  node = gsk_render_node_deserialize (bytes, deserialize_error_func, NULL);
   end = g_get_monotonic_time ();
   if (benchmark)
     {
@@ -78,8 +91,6 @@ main(int argc, char **argv)
 
   if (node == NULL)
     {
-      g_printerr ("Invalid node file: %s\n", error->message);
-      g_clear_error (&error);
       return 1;
     }