Check if ringbuffer is NULL in baseaudiosink's setcaps().
This happened when I swapped the sink on a pipeline.
---

 gst-plugins-base/gst-libs/gst/audio/gstbaseaudiosink.c |    3 +++
 1 files changed, 3 insertions(+)

Index: src/gst-plugins-base/gst-libs/gst/audio/gstbaseaudiosink.c
===================================================================
--- src.orig/gst-plugins-base/gst-libs/gst/audio/gstbaseaudiosink.c
+++ src/gst-plugins-base/gst-libs/gst/audio/gstbaseaudiosink.c
@@ -316,6 +316,9 @@ gst_base_audio_sink_setcaps (GstBaseSink
   GstBaseAudioSink *sink = GST_BASE_AUDIO_SINK (bsink);
   GstRingBufferSpec *spec;
 
+  if (sink->ringbuffer == NULL)
+    return FALSE;
+
   spec = &sink->ringbuffer->spec;
 
   GST_DEBUG_OBJECT (sink, "release old ringbuffer");

-- 
Ville Syrjälä
ville.syrjala@movial.fi