Fix issue https://github.com/nikhilmodak/gulp-ngdocs/issues/22, this happens when gulp-ngdocs does not find any documentation in supplied source
Fix issue https://github.com/nikhilmodak/gulp-ngdocs/issues/22, this happens when gulp-ngdocs does not find any documentation in supplied source

hans-helms/gulp-ngdocs,whitneyit/gulp-ngdocs-manuelro,cpaof/gulp-ngdocs,alizarion/gulp-ngdocs,paul-barry-kenzan/gulp-ngdocs,michaelbazos/gulp-ngdocs,heran/gulp-fakedocs,manuelro/gulp-ngdocs,nikhilmodak/gulp-ngdocs,Thellior/gulp-ngdocs