Don't try to draw if there are no points in the path

In some cases, for instance if drawEllipse() was called with a null QRect
then it would still try to draw a QVectorPath without having enough points
in the list. Therefore the point_count should be checked first before
doing any drawing.

Change-Id: I9b8dbb87c73b74e9df9eb10ec790a484d05d4c46
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>