error_resilience: fix the check for missing references in ff_er_frame_end() for H264

Signed-off-by: Janne Grunau <janne-libav@jannau.net>

libavcodec/error_resilience.c

@@ -652,7 +652,7 @@ static int is_intra_more_likely(MpegEncContext *s){
 
     if(s->codec_id == CODEC_ID_H264){
         H264Context *h= (void*)s;
-        if (h->ref_count[0] <= 0 || !h->ref_list[0][0].f.data[0])
+        if (h->list_count <= 0 || h->ref_count[0] <= 0 || !h->ref_list[0][0].f.data[0])
             return 1;
     }