avcodec/xan: fix style issue

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/xan.c

@@ -556,7 +556,7 @@ static int xan_decode_frame(AVCodecContext *avctx,
         int i;
         tag  = bytestream2_get_le32(&ctx);
         size = bytestream2_get_be32(&ctx);
-        if(size < 0) {
+        if (size < 0) {
             av_log(avctx, AV_LOG_ERROR, "Invalid tag size %d\n", size);
             return AVERROR_INVALIDDATA;
         }