This will likely also fix CID 1452562, a false positive resulting from
Coverity thinking that av_dict_set() automatically frees its key and
value parameters (even without the AV_DICT_DONT_STRDUP_* flags).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>