Merge pull request #1095 from am11/master

Code: Null checks
CompilerRunner: Ignore only when parent's sprite.
Fixes #1082.
Merge pull request #1096 from am11/master

FileHelpers: Avoid BOM (ai/postcss#46)
Merge pull request #1097 from am11/issue-1082

CompilerRunner: Ignore only when parent's sprite