avformat/md5proto: free the MD5 context when opening the output fails

This is not a security issue.

Fixes: ORPoDnVi3BLg
Fixes: swarm-MD5-context-leaked-when-output-URL-open-fails-e4415f

Found-by: zhang xingxing <2388969553@qq.com>

Memory leak Replicated through UnModified FFmpeg with LSAN

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/md5proto.c

@@ -62,6 +62,7 @@ static int md5_close(URLContext *h)
     int err = 0;
 
     av_md5_final(c->md5, md5);
+    av_freep(&c->md5);
     ff_data_to_hex(buf, md5, sizeof(md5), 1);
     buf[2 * sizeof(md5)] = '\n';
 
@@ -80,8 +81,6 @@ static int md5_close(URLContext *h)
             err = AVERROR(errno);
     }
 
-    av_freep(&c->md5);
-
     return err;
 }