Doc parsing fails on @option notation

[dannypurcell]

Adding the following

# @option test_hash [String] :test_opt a Hash test argument

to test/rubycom/util_test_module.rb
and running ./test/rubycom/util_test_bin.rb UtilTestModule test_command_arg_hash --help
results in the following exception

helpers.rb:17:in `block in format_tags': tag[:types]  should be an Array but was NilClass (ArgumentError)