post proc : volume listener : fix effect release crash

Fix access to deleted effect context in vol_prc_lib_release()

Bug: 25753245.
Change-Id: I64ca99e4d5d09667be4c8c605f66700b9ae67949
(cherry picked from commit 93ab6fdda7b7557ccb34372670c30fa6178f8426)
(cherry picked from commit ebbb82365172337c6c250c6cac4e326970a9e351)
1 file changed