libavformat/mov.c: Free aes_decrypt to avoid leaking memory

Found by Chromium fuzzers (crbug.com/1057205).

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit ad91cf1f2f)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -1003,6 +1003,7 @@ static int mov_read_adrm(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     sha = av_sha_alloc();
     if (!sha)
         return AVERROR(ENOMEM);
+    av_free(c->aes_decrypt);
     c->aes_decrypt = av_aes_alloc();
     if (!c->aes_decrypt) {
         ret = AVERROR(ENOMEM);