Fix the bug for updating tasks for which start time equals end time or start date equals end date. Previously, updating the start time or start date will cause the tasks not to update the end time or end date, and the duration of the task will be lengthened, instead of keeping the start time and end time equal, or start date and end date equal. Now updating start time or start date for tasks which have equal start time and end time or start date and end date will cause both the end time and end dates to update to the new time or date also.