QWebEngineView closes immediately after loading

Question

I am having issue using QWebEngineView from Mainwindow. It closes immediately after it opens. Graphical view of my problem

This standalone code is running perfectly:

url = 'https://google.com'

app = QApplication(sys.argv)

# QWebEngineView
iframe = QWebEngineView()
iframe.load(QUrl(url))
iframe.show()

sys.exit(app.exec_())

But when I am adding this feature to my project, the problem arises:

from PySide6.QtWidgets import QMainWindow
from ui_widget import Ui_Widget
from iframe import Iframe

class Widget(QMainWindow, Ui_Widget):
    def __init__(self, app):
        super().__init__()
        self.app = app
        self.setupUi(self)
        self.setWindowTitle('Untitled[*] - Notepad')


        self.actionSend_Feedback.triggered.connect(self.feedback)


    def feedback(self):
        url = 'https://ciomic.com'
        feedback = Iframe(url)
        feedback.show()


from PySide6.QtCore import QUrl
from PySide6.QtWebEngineWidgets import QWebEngineView

class Iframe(QWebEngineView):
    def __init__(self, url):
        super().__init__()
        self.load(QUrl(url))
        self.show()


import sys
from PySide6 import QtWidgets
from widget import Widget
    
app = QtWidgets.QApplication(sys.argv)

window = Widget(app)
window.show()

sys.exit(app.exec())