h264: remove assert() on ref_frame_count.

This assert can fail if a SPS with a smaller value becomes active.
Fixes Ticket532

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

libavcodec/h264_refs.c

@@ -479,10 +479,9 @@ static void print_long_term(H264Context *h) {
 
 void ff_generate_sliding_window_mmcos(H264Context *h) {
     MpegEncContext * const s = &h->s;
-    av_assert0(h->long_ref_count + h->short_ref_count <= h->sps.ref_frame_count);
 
     h->mmco_index= 0;
-    if(h->short_ref_count && h->long_ref_count + h->short_ref_count == h->sps.ref_frame_count &&
+    if(h->short_ref_count && h->long_ref_count + h->short_ref_count >= h->sps.ref_frame_count &&
             !(FIELD_PICTURE && !s->first_field && s->current_picture_ptr->f.reference)) {
         h->mmco[0].opcode= MMCO_SHORT2UNUSED;
         h->mmco[0].short_pic_num= h->short_ref[ h->short_ref_count - 1 ]->frame_num;