motion_est: more complete SAB diamond size check

This makes no difference with the current #defines

Fixes CID732255
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3a48e38ad0)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/motion_est.c

@@ -300,7 +300,7 @@ int ff_init_me(MpegEncContext *s){
     int cache_size= FFMIN(ME_MAP_SIZE>>ME_MAP_SHIFT, 1<<ME_MAP_SHIFT);
     int dia_size= FFMAX(FFABS(s->avctx->dia_size)&255, FFABS(s->avctx->pre_dia_size)&255);
 
-    if(FFMIN(s->avctx->dia_size, s->avctx->pre_dia_size) < -ME_MAP_SIZE){
+    if(FFMIN(s->avctx->dia_size, s->avctx->pre_dia_size) < -FFMIN(ME_MAP_SIZE, MAX_SAB_SIZE)){
         av_log(s->avctx, AV_LOG_ERROR, "ME_MAP size is too small for SAB diamond\n");
         return -1;
     }