QLayout: Attempting to add QLayout XXX to XXX, which already has a layout

QLayout: Attempting to add QLayout "" to studio::FootageListDock "footagelistDock", which already has a layout

FootageListDock::FootageListDock(QWidget* parent)
	: QDockWidget(parent) { 
	setObjectName("footagelistDock");
	setWindowTitle(tr("Footage List")); 
	setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Expanding);
	
	QHBoxLayout* mainLayout = new QHBoxLayout(this);  ## 1
	mFootageList = new FootageListWidget(this);       ## 2
	mFootageList->setRowCount(3);
	mFootageList->setColumnCount(1);
	mFootageList->setItem(0,0,new QTableWidgetItem("Jan"));
	mFootageList->setItem(1,0,new QTableWidgetItem("Feb"));
	mFootageList->setItem(2,0,new QTableWidgetItem("Mar"));
	mFootageList->setRowCount(mFootageList->rowCount() + 1);
	mFootageList->setItem(3,0, new QTableWidgetItem("April"));

	mainLayout->addWidget(mFootageList);
	QWidget* centralWidget = new QWidget(this);
	centralWidget->setLayout(mainLayout);  ## 3
	setWidget(centralWidget);
}