Initialize the new pref field in audiounit_mix_output_buffer

Author: padenot

src/cubeb_audiounit.cpp

@@ -417,7 +417,8 @@ audiounit_mix_output_buffer(cubeb_stream * stm,
     stm->output_stream_params.format,
     stm->output_stream_params.rate,
     CUBEB_CHANNEL_LAYOUT_MAPS[stm->context->layout].channels,
-    stm->context->layout
+    stm->context->layout,
+    CUBEB_STREAM_PREF_NONE
   };
 
   // The downmixing(from 5.1) supports in-place conversion, so we can use