doc/examples/extract_mvs: Explicitly free options

The user should not rely on all options always being recognized
(in particular not on error).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

doc/examples/extract_mvs.c

@@ -104,7 +104,9 @@ static int open_codec_context(AVFormatContext *fmt_ctx, enum AVMediaType type)
 
         /* Init the video decoder */
         av_dict_set(&opts, "flags2", "+export_mvs", 0);
-        if ((ret = avcodec_open2(dec_ctx, dec, &opts)) < 0) {
+        ret = avcodec_open2(dec_ctx, dec, &opts);
+        av_dict_free(&opts);
+        if (ret < 0) {
             fprintf(stderr, "Failed to open %s codec\n",
                     av_get_media_type_string(type));
             return ret;