Update changelog

Author: bouwew

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Anna: remove device availability, fix for https://github.com/home-assistant/core/issues/81716
 - Anna + OnOff device: fix incorrect heating-state, fix for https://github.com/home-assistant/core/issues/81839
 - Improve xml-data missing, raise exception with warning. Solution for https://github.com/home-assistant/core/issues/81672
+- Improve handling of empty schedule, solution for https://github.com/plugwise/python-plugwise/issues/241
 
 # v0.25.9: Adam: hide cooling-related switch, binary_sensors when there is no cooling present
 - This fixes the unexpected appearance of new entities after the Adam 3.7.1 firmware-update