avcodec/motion_est: Set subcmp consistently for H261

Fixes Ticket3150
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/motion_est.c

@@ -321,6 +321,9 @@ int ff_init_me(MpegEncContext *s){
 
     c->avctx= s->avctx;
 
+    if(s->codec_id == AV_CODEC_ID_H261)
+        c->avctx->me_sub_cmp = c->avctx->me_cmp;
+
     if(cache_size < 2*dia_size && !c->stride){
         av_log(s->avctx, AV_LOG_INFO, "ME_MAP size may be a little small for the selected diamond size\n");
     }