Topic: Conditional link to not acting correctly if nil

So here is what I have currently (minus classes, etc. for brevity)

content_tag(:nav, :class => "show_image_nav btn-group") do
  link_to_unless(asset.prev.nil?, "", user_asset_path(asset.prev), :title => "Previous") +
  link_to_unless(asset.next.nil?, "", user_asset_path(asset.next), :title => "Next")
end

This is working as expected IF asset.prev isn't nil OR asset.next isn't nil. I'm at a loss what to do in this situation. My first setup was link_to's inside regular if statements

if asset.prev.nil?
  link_to(bleh)
end +
if asset.next.nil?
  link_to(bleh)
end

Same problems. How do you conditionally concatenate in a helper method?