avformat/movenc: initialize pts/dts of timecode packet

Fix below error message when timecode packet is written.
"Application provided duration: -9223372036854775808 / timestamp: -9223372036854775808 is out of range for mov/mp4 format"

try to reproduce by:
ffmpeg -y -f lavfi -i color -metadata "timecode=00:00:00:00" -t 1 test.mov

Note although error message is printed, the timecode packet will be written anyway. So
the patch 2/2 will try to change the log level to warning.

Fixes ticket #9488

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavformat/movenc.c

@@ -6359,6 +6359,7 @@ static int mov_create_timecode_track(AVFormatContext *s, int index, int src_inde
     pkt->data = data;
     pkt->stream_index = index;
     pkt->flags = AV_PKT_FLAG_KEY;
+    pkt->pts = pkt->dts = av_rescale_q(tc.start, av_inv_q(rate), (AVRational){1,mov->movie_timescale});
     pkt->size = 4;
     AV_WB32(pkt->data, tc.start);
     ret = ff_mov_write_packet(s, pkt);