Problem with SiriAddViews()

[gotnull]

I have a problem with the following code:

object = SiriAddViews.new

object.make_root(last_ref_id)

answer = SiriAnswer.new(program_name, [
    SiriAnswerLine.new("logo", "http://www.ourguide.com.au/images/station_images/#{channel}.png")
])

answer << SiriAnswerLine.new(program_additional_info) unless program_additional_info?

object.views << SiriAnswerSnippet.new([answer])

send_object object

If I remove the following line then it works fine:

answer << SiriAnswerLine.new(program_additional_info) unless program_additional_info?

It actually displays the view, however when I leave that line in. It doesn't display the view and just sits there doing nothing.

Any help would be greatly appreciated as program_additional_info doesn't always contain a value.