huffyuvdec: Check init_vlc() return codes.

      Prevents out of array writes

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit f67a0d115254461649470452058fa3c28c0df294)

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