equalizer: fix out of range test case
equalizer: fix out of range test case

(cherry picked from commit ee77bd03d27f987750aab648016376f58d72f7bf)

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2