Fixed double-logout error, closes #277

server.py

@@ -509,7 +509,7 @@ def login():
 
 @app.route('/internal/logout', methods=['GET', 'POST'])
 def logout():
-	session.pop('user')
+	session.pop('user', None)
 	return redirect(request.values.get('ref', url_for('index')))
 
 @app.route('/internal/auth')