4xmdemux: Check chunk size

Fixes over reading the header array

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 474e31c904f766b6989fe614c3fb093e697c847f)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
1 file changed