Omit empty options in source.list template to fix MODULES-11174
Omit empty options in source.list template to fix MODULES-11174

Empty `[name= ...]` options in a soures list lead to Apt parsing errors.

This change skips such empty options, resolving https://tickets.puppetlabs.com/browse/MODULES-11174.
puppetlabs/puppetlabs-apt