Is this Bugs in webview?

I have a webview, and hosted to 000webhost.
I can save input form into my database when on site.

My form is checking all input first, if there an empty string, the pop up message of website will be return to the missing textinput a.k.a required post

But in my screen, i call the URL of my site in the CustomWebView, i try to fill and giving 1 empty input, this result should be pop up, but my button doesnt work and then i cant go up(scroll) or clicking anything on my webview if not refresh it

This is my blocks, i test it and all good. going to site url ex : link/id=2