Steps to Reproduce

1. add the dependency "org.zkoss.zk:stateless:10.0.0.FL.20240205"
2. open http://localhost:8080/zkdemo/getting_started/tree
3. see cannot read properties of undefined error in browser console
4. click the SUV row but no cars displayed in the table to the right
5. click the caret-right icon beside SUV but no rows displayed under SUV 

1. add the dependency "org.zkoss.zk:stateless:10.0.0.FL.20240205"
2. open http://localhost:8080/zkdemo/event/create_on_demand
3. click [Click me to open the groupbox]
4. see cannot read properties of undefined error in browser console

Current Result

1. cannot read properties of undefined error
2. after clicking the SUV row, no cars displayed in the table to the right
3. after clicking the caret-right icon beside SUV, no rows displayed under SUV

Expected Result

1. no cannot read properties of undefined error
2. after clicking the SUV row, 5 cars displayed in the table to the right
3. after clicking the caret-right icon beside SUV, 2 rows displayed under SUV

Debug Information

the bug exists only when stateless.jar is added

Workaround