When you only have 1 task added, and you complete editing the task, there's no option to 'complete' the edit. You remain in 'edit' mode for the task indefinitely. Clicking away does not do anything, you have to create a new task to exit out of 'edit' mode.
When you have 2 or more tasks, when you click on another task you exit out of 'edit' mode for the first task, but when you have only 1 task, that's not an option.