aspect: don't allow scaled_src_size be 0

It doesn't make sense to have zero here and it breaks, logic below.
Width was still campled to 1, but with broken offset.

This fixes things like video-scale-x=0

video/out/aspect.c

@@ -83,6 +83,7 @@ static void src_dst_split_scaling(int src_size, int dst_size,
                                   int *osd_margin_a, int *osd_margin_b)
 {
     scaled_src_size *= powf(2, zoom) * scale;
+    scaled_src_size = MPMAX(scaled_src_size, 1);
     align = (align + 1) / 2;
 
     *src_start = 0;