Allow ElasticBeanstalk Config Template to not set optionSettings

[yissachar]

If I have a ConfigurationTemplate without optionSettings then it will fail with an NPE:

configurationTemplates {
    production {
         solutionStackName = '64bit Amazon Linux 2016.09 v2.3.1 running Tomcat 8 Java 8'
    }
}

I shouldn't have to provide optionSettings if I am not changing any options. Currently I workaround this by pointing to a file that contains an empty array: [].

[rocboronat]

Thanks for the workaround! :-)