avcodec/mpegvideo: remove extra space

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavcodec/mpegvideo.c

@@ -1112,7 +1112,7 @@ void ff_mpv_common_end(MpegEncContext *s)
     int i;
 
     if (!s)
-        return ;
+        return;
 
     if (s->slice_context_count > 1) {
         for (i = 0; i < s->slice_context_count; i++) {