noise_bsf: fix division by 0

Fixes CID733737
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 93ef29b6f47eda7d73eb9e71628f1f1abb64266d)

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