Adaptive PCM: set the output category (fixes assertion)

modules/codec/adpcm.c

@@ -246,6 +246,7 @@ static int OpenDecoder( vlc_object_t *p_this )
              p_dec->fmt_in.audio.i_bitspersample, p_sys->i_block,
              p_sys->i_samplesperblock );
 
+    p_dec->fmt_out.i_cat = AUDIO_ES;
     p_dec->fmt_out.i_codec = AOUT_FMT_S16_NE;
     p_dec->fmt_out.audio.i_rate = p_dec->fmt_in.audio.i_rate;
     p_dec->fmt_out.audio.i_channels = p_dec->fmt_in.audio.i_channels;