Fixed NPE when pause is complete on a dead app.

            // It is possible the activity was freezing the screen before it was paused.

            // In that case go ahead and remove the freeze this activity has on the screen

            // since it is no longer visible.

            if (prev != null) {

                prev.stopFreezingScreenLocked(true /*force*/);

            }

            mPausingActivity = null;

        }