uridecodebin3: Fix string leak

uri and suburi should be free'd

https://bugzilla.gnome.org/show_bug.cgi?id=795932
diff --git a/gst/playback/gsturidecodebin3.c b/gst/playback/gsturidecodebin3.c
index 436e37c..606fe3d 100644
--- a/gst/playback/gsturidecodebin3.c
+++ b/gst/playback/gsturidecodebin3.c
@@ -652,6 +652,8 @@
   GstURIDecodeBin3 *dec = GST_URI_DECODE_BIN3 (obj);
 
   g_mutex_clear (&dec->lock);
+  g_free (dec->uri);
+  g_free (dec->suburi);
 
   G_OBJECT_CLASS (parent_class)->finalize (obj);
 }