gst: Fix compilation with latest GLib

g_object_ref() forwards the type of its argument nowadays.

./grammar.y:409:14: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]
gstchildproxy.c:212:7: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]
diff --git a/gst/gstchildproxy.c b/gst/gstchildproxy.c
index ca5e47e..1bf983a 100644
--- a/gst/gstchildproxy.c
+++ b/gst/gstchildproxy.c
@@ -209,7 +209,7 @@
   g_return_val_if_fail (GST_IS_CHILD_PROXY (object), FALSE);
   g_return_val_if_fail (name != NULL, FALSE);
 
-  obj = g_object_ref (object);
+  obj = G_OBJECT (g_object_ref (object));
 
   current = names = g_strsplit (name, "::", -1);
   /* find the owner of the property */
diff --git a/gst/parse/grammar.y b/gst/parse/grammar.y
index bc4c3c1..65492ba 100644
--- a/gst/parse/grammar.y
+++ b/gst/parse/grammar.y
@@ -406,7 +406,7 @@
   } else {
     pspec = g_object_class_find_property (G_OBJECT_GET_CLASS (element), value);
     if (pspec != NULL) {
-      target = g_object_ref (element);
+      target = G_OBJECT (g_object_ref (element));
       GST_CAT_LOG_OBJECT (GST_CAT_PIPELINE, target, "found %s property", value);
     } else {
       SET_ERROR (graph->error, GST_PARSE_ERROR_NO_SUCH_PROPERTY, \