avformat/utils: fix mixed declarations and code

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/utils.c

@@ -1734,10 +1734,10 @@ int av_read_frame(AVFormatContext *s, AVPacket *pkt)
 
             if (next_pkt->dts != AV_NOPTS_VALUE) {
                 int wrap_bits = s->streams[next_pkt->stream_index]->pts_wrap_bits;
-                av_assert2(wrap_bits <= 64);
                 // last dts seen for this stream. if any of packets following
                 // current one had no dts, we will set this to AV_NOPTS_VALUE.
                 int64_t last_dts = next_pkt->dts;
+                av_assert2(wrap_bits <= 64);
                 while (pktl && next_pkt->pts == AV_NOPTS_VALUE) {
                     if (pktl->pkt.stream_index == next_pkt->stream_index &&
                         av_compare_mod(next_pkt->dts, pktl->pkt.dts, 2ULL << (wrap_bits - 1)) < 0) {