LineEdit doesn't receive OnTextChanged event when inside a GroupBox

[Raphael Beer]

When adding a declarative LineEdit to a GroupBox, the LineEdit's OnTextChanged handler isn't called.

1. Run below sample code
2. Enter '123' in left LineEdit (both handlers are called)
3. Enter '123' in the right LineEdit, inside the GoupBox (only OnEditingFinished is called)

package main

import (
	"fmt"

	. "github.com/lxn/walk/declarative"
)

func main() {
	MainWindow{
		Title:   "no-onTextChanged-in-groupbox",
		Size:    Size{Width: 400, Height: 100},
		MinSize: Size{Width: 400, Height: 100},
		Layout:  Flow{},
		Children: []Widget{
			LineEdit{
				OnTextChanged: func() {
					fmt.Println("nogroup changed")
				},
				OnEditingFinished: func() {
					fmt.Println("nogroup finished")
				},
			},
			GroupBox{
				Layout: HBox{},
				Children: []Widget{
					LineEdit{
						OnTextChanged: func() {
							fmt.Println("group changed")
						},
						OnEditingFinished: func() {
							fmt.Println("group finished")
						},
					},
				},
			},
		},
	}.Run()
}