avutil/log: Fix context pointer used for get_category()

Fixes calling a random pointer

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
h264_ps: check croping values

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
h264: assert that croping values at slice level are consistent

These values where checked before already.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
h264: Use the correct croping values.

This fixes returning pictures with corrupted data pointers.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>