avcodec/tiff: Check tile_length and tile_width

Fixes: Division by 0
Fixes: 49235/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-5495613847896064

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg


Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 76112c2b)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>