ahssrc is a new plugin that enables Gstreamer to read from the
android.hardware.Sensor Android sensors. These sensors are treated as
buffers and can be passed through and manipulated by the pipeline.
https://bugzilla.gnome.org/show_bug.cgi?id=768110
The frame available callback can be called after deconfiguring the amc codec.
Guard against this by setting the back pointer to NULL on close() and ignoring
any NULL data pointer.
https://bugzilla.gnome.org/show_bug.cgi?id=761014