show include_sender_in_reverse_alias as checked if user hasn't set any value

app/dashboard/templates/dashboard/setting.html

@@ -321,7 +321,8 @@
           <input type="hidden" name="form-name" value="sender-in-ra">
           <div class="form-check">
             <input type="checkbox" id="include-sender-ra" name="enable"
-                {% if current_user.include_sender_in_reverse_alias %} checked {% endif %} class="form-check-input">
+{#                   todo: remove current_user.include_sender_in_reverse_alias is none condition #}
+                {% if current_user.include_sender_in_reverse_alias is none or current_user.include_sender_in_reverse_alias %} checked {% endif %} class="form-check-input">
             <label for="include-sender-ra">Include sender address in reverse-alias</label>
           </div>
           <button type="submit" class="btn btn-outline-primary">Update</button>

server.py

@@ -194,6 +194,7 @@ def fake_data():
         intro_shown=True,
         fido_uuid=None,
     )
+    user.include_sender_in_reverse_alias = None
     db.session.commit()
 
     user.trial_end = None