hevc: Consider first quantization group any reference to 0, 0

According to my understanding of T-REC-H.265-2013044 chapter 8.6.1.

Sample-Id: 00001438-google
Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/hevc_filter.c

@@ -90,7 +90,7 @@ static int get_qPy_pred(HEVCContext *s, int xC, int yC,
     int qPy_pred, qPy_a, qPy_b;
 
     // qPy_pred
-    if (lc->first_qp_group) {
+    if (lc->first_qp_group || (!xQgBase && !yQgBase)) {
         lc->first_qp_group = !lc->tu.is_cu_qp_delta_coded;
         qPy_pred = s->sh.slice_qp;
     } else {