refs #727: don't attempt to read terminated subprocess
refs #727: don't attempt to read terminated subprocess

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