Fixed Sprint Burndown chart not loading on specific instances

Resolved an issue where the Sprint Burndown chart was not loading for certain Jira instances, specifically empty instances with a newly created simple board. The chart now correctly initialises and displays data as expected.

Fixed Cycle Time gadget settings not saving

Fixed an issue where the Cycle Time gadget settings would revert after a refresh, displaying errors in the console. Some widgets worked as expected, but this specific case caused settings to reset. The update ensures that settings are correctly saved and persist after a dashboard refresh.