Clear Timelog Category

When you are adding a time entry to a task, you are given the option to select a category (if enabled). If a user selects a category (by mistake or on purpose), they are unable to clear the category. The category choice persists even if the "reset timer" option is used or if the user navigates away from the time entry/refreshes the page.

I'd like users to be able to clear the time category from the time entry box. For now, I have added a category "none" so the user has an option to unset the category.