REG: Text selection in the text editor example causes the text document to reposition the blocks after the selection

I came across this bug randomly, and I haven't looked very deeply into it yet.

But if you open the Text Editor example in qtdeclarative/examples/quickcontrols2/texteditor and select some text in the text document, you'll notice that some of the blocks are being repositioned, which shouldn't happen. 

The attached video will show the issue, that I've attempted to describe above.

This is a regression from 6.3, where it behaves how you'd expect.
I'm unsure what is causing this to happen, but it looks like the text editor code hasn't been changed between 6.3 and 6.4 in a meaningful way.