Added missing value to Framebuffer::DefaultReadAttachment.
Added missing value to Framebuffer::DefaultReadAttachment.

MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,ashimidashajia/magnum,ashimidashajia/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,ashimidashajia/magnum,DerThorsten/magnum