avcodec/opus: check if internal is available

libavcodec/opus.c

@@ -326,7 +326,9 @@ av_cold int ff_opus_parse_extradata(AVCodecContext *avctx,
         return AVERROR_PATCHWELCOME;
     }
 
-    avctx->delay = avctx->internal->skip_samples = AV_RL16(extradata + 10);
+    avctx->delay = AV_RL16(extradata + 10);
+    if (avctx->internal)
+        avctx->internal->skip_samples = avctx->delay;
 
     channels = avctx->extradata ? extradata[9] : (avctx->channels == 1) ? 1 : 2;
     if (!channels) {