Datebox throws a javascript error when opening it with a mobile browser

Steps to Reproduce

1. run the zul with chrome device simulator, iPad / iPad pro

<datebox>

2. click datebox's button to open it

Current Result

zk.wpd:41616 Uncaught TypeError: this.open is not a function
at init.doClick_ (zk.wpd:41616)
at _doEvt (zk.wpd:24961)
at HTMLDocument.<anonymous> (zk.wpd:25165)
at HTMLDocument.dispatch (zk.wpd:5286)
at HTMLDocument.elemData.handle (zk.wpd:4957)

Expected Result

no error

Debug Information

• 8.0.5 has no such issue
• If you choose Galaxy, this issue doesn't happen

Workaround