[GSUB] Fix reverse lookup loop like we did in the old code before
[GSUB] Fix reverse lookup loop like we did in the old code before

kari-lentz/alpha-pango,danny-ku/pango,kari-lentz/alpha-pango,OpenInkpot-archive/iplinux-pango1.0,kari-lentz/alpha-pango,OpenInkpot-archive/iplinux-pango1.0,zsx/pango,kari-lentz/alpha-pango,OpenInkpot-archive/iplinux-pango1.0,Distrotech/pango,zsx/pango,Distrotech/pango,zsx/pango,zsx/pango,danny-ku/pango,Distrotech/pango,danny-ku/pango