cogl/glx: Silence a compiler warning
cogl/glx: Silence a compiler warning

Distrotech/cogl,djdeath/cogl-android,Distrotech/cogl,djdeath/cogl-android,collects/cogl,collects/cogl,spatulasnout/cogl,spatulasnout/cogl,gcampax/cogl,gcampax/cogl,djdeath/cogl,Distrotech/cogl,gcampax/cogl,Distrotech/cogl,gcampax/cogl,djdeath/cogl,djdeath/cogl-android,djdeath/cogl