PaintEvent warning

This is the situation where i meet this warning.

I have a scene with two QGraphicsRectItem.
I select one of these, and then (manteining the first item selected), I select the other(the first item lost the selection).....

...in this situation the application write in the std output:
"QWidget::repaint: It is dangerous to leave painters active on a widget outside of the PaintEvent"

Is really dangerous? how resolve?

Could you prepare a minimal compilable example reproducing the problem?