fix(plugins): do not return null in posthtml plugin
fix(plugins): do not return null in posthtml plugin

yusufsafak/cerebral,fopsdev/cerebral,christianalfoni/cerebral,bdjnk/cerebral,FWeinb/cerebral,yusufsafak/cerebral,garth/cerebral,idream3/cerebral,cerebral/cerebral,christianalfoni/cerebral,bdjnk/cerebral,FWeinb/cerebral,fopsdev/cerebral,idream3/cerebral,garth/cerebral,cerebral/cerebral