Support APK built with AGP version 8.3

[mathroule]

Context

When parsing an APK built with AGP version 8.3, APK Resource Toolkit raise an error:

undefined method 'key' for nil:NilClass

      return "@#{res_spec.id}/#{entry.values[0].key}"
                                               ^^^^
/vendor/bundle/ruby/3.1.0/gems/apktools-0.7.4/lib/apktools/apkresources.rb:250:in 'get_resource_key'
/vendor/bundle/ruby/3.1.0/gems/apktools-0.7.4/lib/apktools/apkxml.rb:241:in 'parse_xml'

This issues does not happen when parsing an APK built with AGP version 8.2.2.

Changes

• Check if entry values is not empty

[devunwired]

Thanks for your contribution! As you might have noticed, I don't maintain this codebase much anymore. However, I'll see if I can find some time in the next few days to publish a new gem version with this update.