Cast with GST_AMC_SURFACE_TEXTURE_JNI crashes?

Hi,

I'm using master branch on a Rk3229 Android box. My program crashs in the following line of gstamcsurfacetexture-jni.c.

GstAmcSurfaceTextureJNI *self = GST_AMC_SURFACE_TEXTURE_JNI (base);

If I changed the above line, using no cast, my program runs.

GstAmcSurfaceTextureJNI *self = base;

When I look at struct _GstAmcSurfaceTextureJNI, I found it has no parent_instance?

struct _GstAmcSurfaceTextureJNI
{
  jobject jobject;
  gint texture_id;

  jobject listener;
  jmethodID set_context_id;
  GstAmcSurfaceTextureOnFrameAvailableCallback callback;
  gpointer user_data;
};

I do not know GObject good enough to know if it's the cause of the crash.