xdrgen error

xdrgen-err.md

$ ruby -I$HOME/xdrgen/lib ~/xdrgen/bin/xdrgen -o foo -l go Stellar-transaction.x 
/Users/bobglickstein/xdrgen/lib/xdrgen/ast/definitions/union.rb:22:in `resolved_case': undefined method `members' for nil:NilClass (NoMethodError)
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:530:in `block (2 levels) in switch_for'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:527:in `each'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:527:in `block in switch_for'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:526:in `each'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:526:in `switch_for'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:289:in `render_union'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:173:in `render_definition'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:147:in `block in render_nested_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:147:in `each'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:147:in `render_nested_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:160:in `render_definition'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:141:in `block in render_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:141:in `each'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:141:in `render_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:142:in `block in render_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:142:in `each'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:142:in `render_definitions'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/generators/go.rb:12:in `generate'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/compilation.rb:26:in `compile'
	from /Users/bobglickstein/xdrgen/lib/xdrgen/cli.rb:23:in `run'
	from /Users/bobglickstein/xdrgen/bin/xdrgen:5:in `<main>'

The generated output ends here:

// ArmForSwitch returns which field name should be used for storing
// the value for an instance of AllowTrustOpAsset
func (u AllowTrustOpAsset) ArmForSwitch(sw int32) (string, bool) {
switch AssetType(sw) {