avformat/utils: Fix integer overflow with complex time bases in avformat_find_stream_info()

Fixes: signed integer overflow: 2045163756 * 2 cannot be represented in type 'int'
Fixes: Ticket5132

Found-by: tsmith
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/utils.c

@@ -4062,7 +4062,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
             if (!st->r_frame_rate.num) {
                 if (    avctx->time_base.den * (int64_t) st->time_base.num
-                    <= avctx->time_base.num * avctx->ticks_per_frame * (int64_t) st->time_base.den) {
+                    <= avctx->time_base.num * avctx->ticks_per_frame * (uint64_t) st->time_base.den) {
                     av_reduce(&st->r_frame_rate.num, &st->r_frame_rate.den,
                               avctx->time_base.den, (int64_t)avctx->time_base.num * avctx->ticks_per_frame, INT_MAX);
                 } else {