Fix error display on stylesheetpopup.
Fix error display on stylesheetpopup.

Teino1978-Corp/Teino1978-Corp-tilemill,isaacs/tilemill,makinacorpus/tilemill,fxtentacle/tilemill,nyimbi/tilemill,isaacs/tilemill,paulovieira/tilemill-clima,tizzybec/tilemill,fxtentacle/tilemill,MappingKat/tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,tizzybec/tilemill,paulovieira/tilemill-clima,mbrukman/tilemill,fxtentacle/tilemill,florianf/tileoven,mbrukman/tilemill,paulovieira/tilemill-clima,nyimbi/tilemill,nyimbi/tilemill,tizzybec/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,paulovieira/tilemill-clima,florianf/tileoven,florianf/tileoven,tizzybec/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,paulovieira/tilemill-clima,mbrukman/tilemill,nyimbi/tilemill,makinacorpus/tilemill,isaacs/tilemill,Zhao-Qi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,fxtentacle/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,mbrukman/tilemill,Zhao-Qi/tilemill,nyimbi/tilemill,MappingKat/tilemill,tilemill-project/tilemill,tilemill-project/tilemill,fxtentacle/tilemill,mbrukman/tilemill,tizzybec/tilemill,tilemill-project/tilemill