add unsubscribe from all button to inbox

app/templates/users/inbox.html

@@ -13,6 +13,7 @@
   {%- endif -%}
 {%- endset -%}
 {%- call() subheader('Your inbox', topline) -%}
+{%- if subscriptions -%}
 <fieldset class="plank even no-shadow minimal subheader-actions">
   <legend>Actions</legend>
   <form method="POST" action="{{url_for('threads.mark_read')}}">
@@ -25,6 +26,7 @@
     <button class="warn">Unsubscribe from all</button>
   </form>
 </fieldset>
+{%- endif -%}
 {%- endcall -%}
 {%- if subscriptions | length > 0 -%}
 <div class="plank">