truemotion1: Check index, fix out of array read

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit fd4c1c0b70b5a06dd572d7e27799a2f4c3d9b984)

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