Убрать отступ между виджетами в QHBoxLayout

Внешний вид приложения

Как видно, список кнопок слева от основного окна отделяет светлая полоса. Я ничерта не понимаю, откуда она взялась и как ее убрать. Подскажите плз.

app.py

import sys
from PySide2 import QtWidgets
from UI_test import Ui_Form

class App(QtWidgets.QWidget):
    def __init__(self, parent = None):
        QtWidgets.QWidget.__init__(self, parent)
        self.ui = Ui_Form()
        self.ui.setupUi(self)


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = App()
    File = open("styles/style.qss",'r')
    with File:
        qss = File.read()
    app.setStyleSheet(qss)
    window.show()
    sys.exit(app.exec_())

style.qss

QListWidget, QListView, QTreeWidget, QTreeView {
outline: 0px;
    }
QListWidget {
    min-width: 120px;
    max-width: 180px;
    color: white;
    background: rgb(30, 30, 30);
}
QListWidget::item:selected {
    background: rgb(168, 71, 245);
   /* border-left: 2px solid rgb(9, 187, 7);*/
}
HistoryPanel::item:hover {background: rgb(52, 52, 52);}
QStackedWidget {background: rgb(30, 30, 30);}
QLabel {color: white;}
QLabel#mainPic {border-style: solid; border-width: 2px;  background-color:#757575;}
QListWidget {background-color: #454e5e;
    color: rgb(30, 30, 30);
    font-size: 12px;
    font-weight: bold;
    border: 1px solid #191919;
    show-decoration-selected: 0;
    padding-left: -13px;
    padding-right: -13px;}

QListWidget::item
{
color: #31cecb;
background-color: #454e5e;
border: none;
padding: 5px;
border-radius: 0px;
padding-left : 10px;
height: 42px;
}
QListWidget::item:selected
{
color: rgb(143, 58, 132);
background-color: #31cecb;
}
QListWidget::item:!selected
{
color:white;
background-color: transparent;
border: none;
padding-left : 10px;
}

QListWidget::item:!selected:hover
{
color: black;
background-color: #bcbdbb;
border: none;
padding-left : 10px;
}

UI_test.py

from PySide2 import QtCore, QtGui, QtWidgets
from PySide2.QtCore import Qt
from random import randint

class Ui_Form(object):
    def setupUi(self, Form):
        Form.resize(1300, 700)
        self.layout = QtWidgets.QHBoxLayout()
        self.layout.setContentsMargins(0, 0, 0, 0)
        self.listWidget = QtWidgets.QListWidget()
        self.layout.addWidget(self.listWidget)
        self.stackedWidget = QtWidgets.QStackedWidget()
        self.layout.addWidget(self.stackedWidget)
        self.listWidget.currentRowChanged.connect(
            self.stackedWidget.setCurrentIndex)

        item1 = QtWidgets.QListWidgetItem(QtGui.QIcon('icons/settings.png'),'CamSettings', self.listWidget)
        item2 = QtWidgets.QListWidgetItem(QtGui.QIcon('icons/explore.png'),'Explore', self.listWidget)
        item3 = QtWidgets.QListWidgetItem(QtGui.QIcon('icons/models.png'),'Models', self.listWidget)
        item4 = QtWidgets.QListWidgetItem(QtGui.QIcon('icons/live.png'),'Live', self.listWidget)

        item1.setSizeHint(QtCore.QSize(10, 60))
        item2.setSizeHint(QtCore.QSize(10, 60))
        item3.setSizeHint(QtCore.QSize(10, 60))
        item4.setSizeHint(QtCore.QSize(10, 60))

        item1.setTextAlignment(QtCore.Qt.AlignCenter)
        item2.setTextAlignment(QtCore.Qt.AlignCenter)
        item3.setTextAlignment(QtCore.Qt.AlignCenter)
        item4.setTextAlignment(QtCore.Qt.AlignCenter)

        label1 = QtWidgets.QLabel('Это страница 1')
        label2= QtWidgets.QLabel('Это страница 2')
        label3 = QtWidgets.QLabel('Это страница 3')
        label4 = QtWidgets.QLabel('Это страница 4')
        
        label1.setAlignment(QtCore.Qt.AlignCenter)
        label2.setAlignment(QtCore.Qt.AlignCenter)
        label3.setAlignment(QtCore.Qt.AlignCenter)
        label4.setAlignment(QtCore.Qt.AlignCenter)

        label1.setStyleSheet('background: rgb(%d, %d, %d); margin: 50px;' % (
            randint(0, 255), randint(0, 255), randint(0, 255)))
        label2.setStyleSheet('background: rgb(%d, %d, %d); margin: 50px;' % (
            randint(0, 255), randint(0, 255), randint(0, 255)))
        label3.setStyleSheet('background: rgb(%d, %d, %d); margin: 50px;' % (
            randint(0, 255), randint(0, 255), randint(0, 255)))
        label4.setStyleSheet('background: rgb(%d, %d, %d); margin: 50px;' % (
            randint(0, 255), randint(0, 255), randint(0, 255)))

        self.image_main = QtWidgets.QLabel()
        self.image_main.setObjectName('mainPic')
        self.image_main.setFixedSize(512, 512)
        pixmap_main = QtGui.QPixmap()
        self.image_main.setPixmap(pixmap_main)
        self.image_main.adjustSize()

        self.slider_all_layers = QtWidgets.QSlider()
        self.slider_all_layers.setOrientation(QtCore.Qt.Horizontal)
        self.slider_all_layers.setMinimum(0)
        self.slider_all_layers.setMaximum(100)
        self.slider_all_layers.setFixedWidth(500)

        button_json = QtWidgets.QPushButton("Create JSON")
        button_json.setFixedWidth(200)

        first_panel_left = QtWidgets.QVBoxLayout()
        first_panel_left.setAlignment(Qt.AlignTop)
        #first_panel_left.addWidget(button_json)

        first_panel_frame_left = QtWidgets.QFrame()
        first_panel_frame_left.setMinimumWidth(200)
        first_panel_frame_left.setLayout(first_panel_left)

        first_panel_right = QtWidgets.QVBoxLayout()
        first_panel_right.addWidget(self.image_main)
        first_panel_right.addWidget(self.slider_all_layers)
        first_panel_right.addStretch()

        first_panel_frame_right = QtWidgets.QFrame()
        first_panel_frame_right.setLayout(first_panel_right)

        main_first_box = QtWidgets.QHBoxLayout()
        main_first_box.addWidget(first_panel_frame_left)
        main_first_box.addWidget(first_panel_frame_right)

        first_container = QtWidgets.QWidget()
        first_container.setLayout(main_first_box)

        self.stackedWidget.addWidget(first_container)
        self.stackedWidget.addWidget(label2)
        self.stackedWidget.addWidget(label3)
        self.stackedWidget.addWidget(label4)
        Form.setLayout(self.layout)