h264: clean all non null elements of delayed_pic[]

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 66ce282df5)

libavcodec/h264.c

@@ -2233,7 +2233,7 @@ static void idr(H264Context *h){
 static void flush_dpb(AVCodecContext *avctx){
     H264Context *h= avctx->priv_data;
     int i;
-    for(i=0; i<MAX_DELAYED_PIC_COUNT; i++) {
+    for(i=0; i<=MAX_DELAYED_PIC_COUNT; i++) {
         if(h->delayed_pic[i])
             h->delayed_pic[i]->reference= 0;
         h->delayed_pic[i]= NULL;