Fix drawing outlines of null-width shapes

If a shape has null width it doesn't mean we shouldn't paint its outline.
Transformations and polygons work with such "empty" rects correctly,
see a special test for it in KisAlgebra2DTest::testNullRectProcessing().

(cherry picked from commit 8be443cbf667ee691fdc964e6defcb028b0251b5)