avcodec/hevc_refs: Silence "Could not find ref with POC" for CRA/BLA

Avoids error messages during seeking

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

libavcodec/hevc_refs.c

@@ -386,6 +386,7 @@ static HEVCFrame *find_ref_idx(HEVCContext *s, int poc)
         }
     }
 
+    if (s->nal_unit_type != NAL_CRA_NUT && !IS_BLA(s))
         av_log(s->avctx, AV_LOG_ERROR,
                "Could not find ref with POC %d\n", poc);
     return NULL;