Handle missing input file gracefully. trac#41  http://reviewboard/r/540/
Handle missing input file gracefully.
trac#41  http://reviewboard/r/540/


git-svn-id: 93cebb81a0f5cc00f31a7ad40d16024532691b70@344 a3683778-fedd-11de-87c3-653bb6514e15

lgritz/OpenShadingLanguage,svenstaro/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,gzorin/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,brechtvl/OpenShadingLanguage,juvenal/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,rlmh/OpenShadingLanguage,mcanthony/OpenShadingLanguage,svenstaro/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,Anteru/OpenShadingLanguage,mcanthony/OpenShadingLanguage,brechtvl/OpenShadingLanguage,brechtvl/OpenShadingLanguage,lgritz/OpenShadingLanguage,svenstaro/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,gzorin/OpenShadingLanguage,juvenal/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,aconty/OpenShadingLanguage,svenstaro/OpenShadingLanguage,brechtvl/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,sjparker/OpenShadingLanguage,imageworks/OpenShadingLanguage,lgritz/OpenShadingLanguage,mcanthony/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,sjparker/OpenShadingLanguage,aconty/OpenShadingLanguage,Anteru/OpenShadingLanguage,rlmh/OpenShadingLanguage,gzorin/OpenShadingLanguage,gzorin/OpenShadingLanguage,imageworks/OpenShadingLanguage,rlmh/OpenShadingLanguage,Anteru/OpenShadingLanguage,gzorin/OpenShadingLanguage,aconty/OpenShadingLanguage,juvenal/OpenShadingLanguage,brechtvl/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,imageworks/OpenShadingLanguage,sjparker/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,lgritz/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,imageworks/OpenShadingLanguage,rlmh/OpenShadingLanguage,lgritz/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,sjparker/OpenShadingLanguage,Anteru/OpenShadingLanguage,juvenal/OpenShadingLanguage,aconty/OpenShadingLanguage,mcanthony/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,imageworks/OpenShadingLanguage,aconty/OpenShadingLanguage