Version
3.0.0-beta.7
Environment
chrome
Reproduction link

Steps to reproduce
input any value of items and then click button
What is expected?
the corresponding error message disappeared
What is actually happening?
value comes out to be "undefined"
Not sure why, I cannot really startup the demo correctly, but the Point is when the valus of input changes, the logs are always undeifined. Please help to check it.