avcodec/svq1enc: Do not print debug RD value before it has been computed

Avoids floating point division by 0

Fixes: Ticket8191

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/svq1enc.c

@@ -486,6 +486,7 @@ static av_cold int svq1_encode_end(AVCodecContext *avctx)
     SVQ1EncContext *const s = avctx->priv_data;
     int i;
 
+    if (avctx->frame_number)
         av_log(avctx, AV_LOG_DEBUG, "RD: %f\n",
                s->rd_total / (double)(avctx->width * avctx->height *
                                       avctx->frame_number));