Fixes a few PLC/DTX bugs due to the recent decode API change

celt @ 1a8bf37d

-Subproject commit 6f6e8b39842a7d175e89f47e4d37ad5de8143ad2
+Subproject commit 1a8bf37dbaa461d410c101d1be302a67b4927035

src/opus_decoder.c

@@ -216,8 +216,9 @@ static int opus_decode_frame(OpusDecoder *st, const unsigned char *data,
             /* Shrink decoder because of raw bits */
             dec.storage -= redundancy_bytes;
         }
-        start_band = 17;
     }
+    if (mode != MODE_CELT_ONLY)
+    	start_band = 17;
 
     if (mode != MODE_SILK_ONLY)
     {
@@ -343,7 +344,9 @@ int opus_decode(OpusDecoder *st, const unsigned char *data,
 	unsigned char ch, toc;
 	/* 48 x 2.5 ms = 120 ms */
 	short size[48];
-	if (len<1)
+	if (len==0 || data==NULL)
+	    return opus_decode_frame(st, NULL, 0, pcm, frame_size, 0);
+	else if (len<0)
 		return CELT_BAD_ARG;
 	st->mode = opus_packet_get_mode(data);
 	st->bandwidth = opus_packet_get_bandwidth(data);

src/opus_encoder.c

@@ -293,6 +293,9 @@ int opus_encode(OpusEncoder *st, const short *pcm, int frame_size,
             fprintf (stderr, "SILK encode error: %d\n", ret);
             /* Handle error */
         }
+        if (nBytes==0)
+            return 0;
+
         /* Extract SILK internal bandwidth for signaling in first byte */
         if( st->mode == MODE_SILK_ONLY ) {
             if( st->silk_mode.internalSampleRate == 8000 ) {

src/test_opus.c

@@ -285,13 +285,13 @@ int main(int argc, char *argv[])
 #if OPUS_TEST_RANGE_CODER_STATE
       enc_final_range[toggle] = opus_encoder_get_final_range( enc );
 #endif
-      if (len[toggle] <= 0)
+      if (len[toggle] < 0)
       {
          fprintf (stderr, "opus_encode() returned %d\n", len[toggle]);
          return 1;
       }
 
-      lost = rand()%100<packet_loss_perc;
+      lost = rand()%100<packet_loss_perc || len[toggle]==0;
       if( count >= use_inbandfec ) {
           /* delay by one packet when using in-band FEC */
           if( use_inbandfec  ) {