avcodec/mpegvideo: Set err on failure in ff_mpv_common_frame_size_change()

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

libavcodec/mpegvideo.c

@@ -1487,7 +1487,7 @@ int ff_mpv_common_frame_size_change(MpegEncContext *s)
         s->mb_height = (s->height + 15) / 16;
 
     if ((s->width || s->height) &&
-        av_image_check_size(s->width, s->height, 0, s->avctx))
+        (err = av_image_check_size(s->width, s->height, 0, s->avctx)) < 0)
         goto fail;
 
     if ((err = init_context_frame(s)))
@@ -1504,7 +1504,7 @@ int ff_mpv_common_frame_size_change(MpegEncContext *s)
             }
 
             for (i = 0; i < nb_slices; i++) {
-                if (init_duplicate_context(s->thread_context[i]) < 0)
+                if ((err = init_duplicate_context(s->thread_context[i])) < 0)
                     goto fail;
                     s->thread_context[i]->start_mb_y =
                         (s->mb_height * (i) + nb_slices / 2) / nb_slices;