Don’t allow user to send texts without template

app/templates/views/choose-sms-template.html

@@ -12,6 +12,7 @@
 
     <h1 class="heading-large">Send text messages</h1>
 
+    {% if templates %}
       <fieldset class='form-group'>
         {% for template in templates %}
           {{ sms_message(
@@ -19,8 +20,15 @@
           ) }}
         {% endfor %}
       </fieldset>
-
       {{ page_footer("Continue") }}
+    {% else %}
+      {{ banner(
+        '<a href="{}">Add a text message template</a> to start sending messages'.format(
+          url_for(".add_service_template", service_id=service_id)
+        )|safe,
+        type="tip"
+      )}}
+    {% endif %}
 
   </form>
 {% endblock %}