flac: infinite loop with fuzzed file

[jrummell]

Summary of the bug:
The attached file (generated by Chrome's fuzzers) causes an infinite loop. Original bug ​https://crbug.com/714370

How to reproduce:

ffmpeg -i testcase.flac dummy.mp4
ffmpeg version N-87069-g1e34019d62 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  configuration: ...
  libavutil      55. 74.100 / 55. 74.100
  libavcodec     57.103.100 / 57.103.100
  libavformat    57. 77.100 / 57. 77.100
  libavdevice    57.  7.101 / 57.  7.101
  libavfilter     6.100.100 /  6.100.100
  libswscale      4.  7.103 /  4.  7.103
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
[flac @ 0x3397360] Format flac detected only with low score of 13, misdetection possible!
...
[NULL @ 0x2d998a0] crc check failed from offset 0 (frame 1) to 6 (frame 1)
[NULL @ 0x2d998a0] sample/frame number mismatch in adjacent frames

In tracing through the code flac_parse() gets a buffer of 2 bytes, and ends up in handle_error:, returning 0. Code in parse_packet() detects that nothing is returned, and tries to parse the same 2 bytes again.

[Carl Eugen Hoyos]

Duplicate of ticket #6112.