In my opinion, organizing tasks in folders is a poor design choice. A filtering approach (e.g. like that of redmine) would be better. On another note, an empty folder shouldn't exist at all.
In folders it'd be useful to show that there are "3 docs" inside. This is especially useful in tools such as Tasks, where we have predefined folders (e.g. "Long-term tasks") that might be empty. Locating which folders are empty save clicks.