fixed a potential error in harmonics when axis=-1
fixed a potential error in harmonics when axis=-1

ruohoruotsi/librosa,Cortexelus/librosa,stefan-balke/librosa,stefan-balke/librosa,ruohoruotsi/librosa,stefan-balke/librosa,ruohoruotsi/librosa,r9y9/librosa,r9y9/librosa,carlthome/librosa,Cortexelus/librosa,r9y9/librosa,Cortexelus/librosa,carlthome/librosa,carlthome/librosa