version 2.1.0
QCPItems are not shown in new polar plots.

	ui.plot->plotLayout()->clear();
	auto* polarAxis = new QCPPolarAxisAngular(ui.plot);
	auto* radAxis = new QCPPolarAxisRadial(polarAxis);
	ui.plot->plotLayout()->addElement(0, 0, polarAxis);
	
	polarAxis->setAngle(0);
	polarAxis->setRangeReversed(true);
	polarAxis->radialAxis(0)->setAngle(10);

	auto* itemLine = new QCPItemLine(ui.plot);
	itemLine->start->setCoords(0, 4);
	itemLine->end->setCoords(0, 2);

err mesg
class QCPAxisRect *__cdecl QCustomPlot::axisRect(int) const invalid axis rect index 0
class QCPAxisRect *__cdecl QCustomPlot::axisRect(int) const invalid axis rect index 0
class QPointF __cdecl QCPItemPosition::pixelPosition(void) const Item position type x is ptPlotCoords, but no axes were defined
class QPointF __cdecl QCPItemPosition::pixelPosition(void) const Item position type y is ptPlotCoords, but no axes were defined
class QPointF __cdecl QCPItemPosition::pixelPosition(void) const Item position type x is ptPlotCoords, but no axes were defined
class QPointF __cdecl QCPItemPosition::pixelPosition(void) const Item position type y is ptPlotCoords, but no axes were defined