Add failing test assertion.
Add failing test assertion.

Apparently this code never tested the code path for colour images.

chrishokamp/fuel,janchorowski/fuel,dmitriy-serdyuk/fuel,codeaudit/fuel,codeaudit/fuel,bouthilx/fuel,orhanf/fuel,dribnet/fuel,hantek/fuel,bouthilx/fuel,aalmah/fuel,udibr/fuel,mila-udem/fuel,aalmah/fuel,dhruvparamhans/fuel,glewis17/fuel,capybaralet/fuel,vdumoulin/fuel,harmdevries89/fuel,mila-udem/fuel,chrishokamp/fuel,mjwillson/fuel,hantek/fuel,capybaralet/fuel,glewis17/fuel,dhruvparamhans/fuel,udibr/fuel,markusnagel/fuel,orhanf/fuel,markusnagel/fuel,mjwillson/fuel,dmitriy-serdyuk/fuel,harmdevries89/fuel,vdumoulin/fuel,janchorowski/fuel,dribnet/fuel