avcodec/mpegvideo_enc: return proper error instead of failing assertion when max rate is not set

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

libavcodec/mpegvideo_enc.c

@@ -388,8 +388,7 @@ av_cold int ff_MPV_encode_init(AVCodecContext *avctx)
 
     if ((!avctx->rc_max_rate) != (!avctx->rc_buffer_size)) {
         av_log(avctx, AV_LOG_ERROR, "Either both buffer size and max rate or neither must be specified\n");
-        if (avctx->rc_max_rate && !avctx->rc_buffer_size)
-            return -1;
+        return -1;
     }
 
     if (avctx->rc_min_rate && avctx->rc_max_rate != avctx->rc_min_rate) {