Fix memory leak

introduced in 8e130d9b06ce8300c46dd80e014f7ae9829733ac
Re-sync FFmpeg copy to release/2.2 branch

branch version: n2.2.2-30-gacafd18

new in 2.2:
- HNM version 4 demuxer and video decoder
- Live HDS muxer
- setsar/setdar filters now support variables in ratio expressions
- elbg filter
- string validation in ffprobe
- support for decoding through VDPAU in ffmpeg (the -hwaccel option)
- complete Voxware MetaSound decoder
- remove mp3_header_compress bitstream filter
- Windows resource files for shared libraries
- aeval filter
- stereoscopic 3d metadata handling
- WebP encoding via libwebp
- ATRAC3+ decoder
- VP8 in Ogg demuxing
- side & metadata support in NUT
- framepack filter
- XYZ12 rawvideo support in NUT
- Exif metadata support in WebP decoder
- OpenGL device
- Use metadata_header_padding to control padding in ID3 tags (currently used in
  MP3, AIFF, and OMA files), FLAC header, and the AVI "junk" block.
- Mirillis FIC video decoder
- Support DNx444
- libx265 encoder
- dejudder filter
- Autodetect VDA like all other hardware accelerations

New in 2.1:
- aecho filter
- perspective filter ported from libmpcodecs
- ffprobe -show_programs option
- compand filter
- RTMP seek support
- when transcoding with ffmpeg (i.e. not streamcopying), -ss is now accurate
  even when used as an input option. Previous behavior can be restored with
  the -noaccurate_seek option.
- ffmpeg -t option can now be used for inputs, to limit the duration of
  data read from an input file
- incomplete Voxware MetaSound decoder
- read EXIF metadata from JPEG
- DVB teletext decoder
- phase filter ported from libmpcodecs
- w3fdif filter
- Opus support in Matroska
- FFV1 version 1.3 is stable and no longer experimental
- FFV1: YUVA(444,422,420) 9, 10 and 16 bit support
- changed DTS stream id in lavf mpeg ps muxer from 0x8a to 0x88, to be
  more consistent with other muxers.
- adelay filter
- pullup filter ported from libmpcodecs
- ffprobe -read_intervals option
- Lossless and alpha support for WebP decoder
- Error Resilient AAC syntax (ER AAC LC) decoding
- Low Delay AAC (ER AAC LD) decoding
- mux chapters in ASF files
- SFTP protocol (via libssh)
- libx264: add ability to encode in YUVJ422P and YUVJ444P
- Fraps: use BT.709 colorspace by default for yuv, as reference fraps decoder does
- make decoding alpha optional for prores, ffv1 and vp6 by setting
  the skip_alpha flag.
- ladspa wrapper filter
- native VP9 decoder
- dpx parser
- max_error_rate parameter in ffmpeg
- PulseAudio output device
- ReplayGain scanner
- Enhanced Low Delay AAC (ER AAC ELD) decoding (no LD SBR support)
- Linux framebuffer output device
- HEVC decoder, raw HEVC demuxer, HEVC demuxing in TS, Matroska and MP4
- mergeplanes filter

New in 2.0:
- curves filter
- reference-counting for AVFrame and AVPacket data
- ffmpeg now fails when input options are used for output file
  or vice versa
- support for Monkey's Audio versions from 3.93
- perms and aperms filters
- audio filtering support in ffplay
- 10% faster aac encoding on x86 and MIPS
- sine audio filter source
- WebP demuxing and decoding support
- new ffmpeg options -filter_script and -filter_complex_script, which allow a
  filtergraph description to be read from a file
- OpenCL support
- audio phaser filter
- separatefields filter
- libquvi demuxer
- uniform options syntax across all filters
- telecine filter
- new interlace filter
- smptehdbars source
- inverse telecine filters (fieldmatch and decimate)
- colorbalance filter
- colorchannelmixer filter
- The matroska demuxer can now output proper verbatim ASS packets. It will
  become the default at the next libavformat major bump.
- decent native animated GIF encoding
- asetrate filter
- interleave filter
- timeline editing with filters
- vidstabdetect and vidstabtransform filters for video stabilization using
  the vid.stab library
- astats filter
- trim and atrim filters
- ffmpeg -t and -ss (output-only) options are now sample-accurate when
  transcoding audio
- Matroska muxer can now put the index at the beginning of the file.
- extractplanes filter
- avectorscope filter
- ADPCM DTK decoder
- ADP demuxer
- RSD demuxer
- RedSpark demuxer
- ADPCM IMA Radical decoder
- zmq filters
- DCT denoiser filter (dctdnoiz)
- Wavelet denoiser filter ported from libmpcodecs as owdenoise (formerly "ow")
- Apple Intermediate Codec decoder
- Escape 130 video decoder
- FTP protocol support
- V4L2 output device
- 3D LUT filter (lut3d)
- SMPTE 302M audio encoder
- support for slice multithreading in libavfilter
- Hald CLUT support (generation and filtering)
- VC-1 interlaced B-frame support
- support for WavPack muxing (raw and in Matroska)
- XVideo output device
- vignette filter
- True Audio (TTA) encoder
- Go2Webinar decoder
- mcdeint filter ported from libmpcodecs
- sab filter ported from libmpcodecs
- ffprobe -show_chapters option
- WavPack encoding through libwavpack
- rotate filter
- spp filter ported from libmpcodecs
- libgme support
- psnr filter

Still using some re-activated old API (in particular avcodec_audio_decode)