tree update model performance

Steps to Reproduce

run the attached example tree-model-replace-performance_zk4803.zul
click the button to replace the tree model

Current Result

The initial rendering is as fast as expected:

Updating the model with the same number of nodes takes significantly longer

Increasing the number of items leads to browser warning about unresponsive scripts.

Expected Result

Similar times to initial and updated tree item rendering.

Debug Information

Workaround

call tree.invalidate() after replacing the model