framebuffer: Bail out if the viewport has negative size
framebuffer: Bail out if the viewport has negative size

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