Ensure only one <h1> per page, even with errors

A page should have only one `<h1>` element. So if there’s an error
message, which contains a `<h1>`, it should replace the page’s normal
`<h1>` element, rather than sit above it.

app/templates/views/api/keys.html

@@ -23,9 +23,6 @@
       {% endcall %}
     </div>
   {% else %}
-
-  {% endif %}
-
     <div class="grid-row">
       <div class="column-two-thirds">
         <h1 class="heading-large">
@@ -36,6 +33,8 @@
         <a href="{{ url_for('.create_api_key', service_id=current_service.id) }}" class="button align-with-heading">Create an API key</a>
       </div>
     </div>
+  {% endif %}
+
   <div class="body-copy-table">
     {% call(item, row_number) list_table(
       keys,

app/templates/views/templates/template.html

@@ -27,9 +27,7 @@
         </form>
       {% endcall %}
     </div>
-  {% endif %}
+  {% elif template_delete_confirmation_message %}
-
-  {% if template_delete_confirmation_message %}
     <div class="bottom-gutter">
       {% call banner_wrapper(type='dangerous', subhead=template_delete_confirmation_message[0]) %}
         <p>
@@ -41,9 +39,9 @@
         </form>
       {% endcall %}
     </div>
-  {% endif %}
+  {% else %}
-
     <h1 class="heading-large">{{ template.name }}</h1>
+  {% endif %}
 
   <div class="grid-row">
     {% with show_title=False, expanded=True %}