avfilter/vf_aspect: Fix integer overflow in compute_dar()

Fixes: signed integer overflow: 1562273630 * 17 cannot be represented in type 'int'
Fixes: Ticket8323

Found-by: Suhwan
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 0c0ca0f244b823238e5a4f5584168e620da84899)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_aspect.c

@@ -104,7 +104,7 @@ static int filter_frame(AVFilterLink *link, AVFrame *frame)
 static inline void compute_dar(AVRational *dar, AVRational sar, int w, int h)
 {
     if (sar.num && sar.den) {
-        av_reduce(&dar->num, &dar->den, sar.num * w, sar.den * h, INT_MAX);
+        av_reduce(&dar->num, &dar->den, sar.num * (int64_t)w, sar.den * (int64_t)h, INT_MAX);
     } else {
         av_reduce(&dar->num, &dar->den, w, h, INT_MAX);
     }