If a single fragment contains more than one frame unit, the tile information stored
in the private context will only correspond to one of them.
Fixes: crash (out of array access)
Fixes: 435489659/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APV_fuzzer-6194885205229568
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: James Almer <jamrial@gmail.com>
