flac: don't overwrite bitspersample

The decoder might have filters in place that cause it to output to
something else than s16n

Close: #6400

modules/codec/flac.c

@@ -233,8 +233,9 @@ static void DecoderMetadataCallback( const FLAC__StreamDecoder *decoder,
     p_dec->fmt_out.audio.i_physical_channels =
         p_dec->fmt_out.audio.i_original_channels =
             pi_channels_maps[metadata->data.stream_info.channels];
-    p_dec->fmt_out.audio.i_bitspersample =
-        metadata->data.stream_info.bits_per_sample;
+    if (!p_dec->fmt_out.audio.i_bitspersample)
+        p_dec->fmt_out.audio.i_bitspersample =
+            metadata->data.stream_info.bits_per_sample;
 
     msg_Dbg( p_dec, "channels:%d samplerate:%d bitspersamples:%d",
              p_dec->fmt_out.audio.i_channels, p_dec->fmt_out.audio.i_rate,