rtmpproto: Consistently use the right prev_pkt array

prev_pkt[0] is used for input packets, while prev_pkt[1] is
used for output.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtmpproto.c

@@ -406,7 +406,7 @@ static int read_connect(URLContext *s, RTMPContext *rt)
     GetByteContext gbc;
 
     if ((ret = ff_rtmp_packet_read(rt->stream, &pkt, rt->in_chunk_size,
-                                   rt->prev_pkt[1])) < 0)
+                                   rt->prev_pkt[0])) < 0)
         return ret;
     cp = pkt.data;
     bytestream2_init(&gbc, cp, pkt.size);