Steps to Reproduce

1. Create a StatelessRichlet with a RichletMapping("/")
2. Add a index() method to map with RichletMapping("")
3. Start a server to visit "/" page (i.e. "http://localhost:8080/myapp/")

Current Result

The index() method in a Class extended from StatelessRichlet doesn't be invoked.

Expected Result

The index() method should be invoked.

Debug Information

The Https.sanitizePath() cannot process a single "/" as its value, so it will return a null path that will be returned directly. - https://github.com/zkoss/zk/blob/44af50a04644dff03941bb7568cea55e5dfe3617/zk/src/main/java/org/zkoss/zk/ui/http/RichletFilter.java#L143

Workaround

Avoid to use RichletMapping("/") on Class. Instead, using "/foo" or "/anything" to workaround this issue.