H264: fix index range assert() in remove_short_at_index()

Originally committed as revision 14233 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -3348,7 +3348,7 @@ static Picture * find_short(H264Context *h, int frame_num, int *idx){
  * @param i index into h->short_ref of picture to remove.
  */
 static void remove_short_at_index(H264Context *h, int i){
-    assert(i > 0 && i < h->short_ref_count);
+    assert(i >= 0 && i < h->short_ref_count);
     h->short_ref[i]= NULL;
     if (--h->short_ref_count)
         memmove(&h->short_ref[i], &h->short_ref[i+1], (h->short_ref_count - i)*sizeof(Picture*));