the example uses the new flash component that is generated into your project on phoenix master, but the solution either way is to conditionally render the flash container, ie you can do:
<%= if msg = live_flash(@flash, :info) do %>
<p class="alert alert-info" role="alert" phx-click="lv:clear-flash" phx-value-key="info">
<%= msg %>
</p>
<% end %>
