Resolve "Better error message if there are no matching lesson periods"

Closes #86 (closed)

aleksis/apps/alsijil/templates/alsijil/class_register/week_view.html

@@ -118,11 +118,11 @@
     <div class="card red darken-1">
       <div class="card-content white-text">
         <span class="card-title">
-          {% blocktrans %}No group selected{% endblocktrans %}
+          {% blocktrans %}No lessons available{% endblocktrans %}
         </span>
         <p>
           {% blocktrans %}
-            There are no lessons for the selected group, teacher or time.
+            There are no lessons for the selected group or teacher in this week.
           {% endblocktrans %}
         </p>
       </div>