smacker: Don't return packets in unallocated streams

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/smacker.c

@@ -344,6 +344,8 @@ static int smacker_read_packet(AVFormatContext *s, AVPacket *pkt)
         smk->cur_frame++;
         smk->nextpos = avio_tell(s->pb);
     } else {
+        if (smk->stream_id[smk->curstream] < 0)
+            return AVERROR_INVALIDDATA;
         if (av_new_packet(pkt, smk->buf_sizes[smk->curstream]))
             return AVERROR(ENOMEM);
         memcpy(pkt->data, smk->bufs[smk->curstream], smk->buf_sizes[smk->curstream]);