NumberAnimation on enter/exit of Dialog is not working correctly with starting/ending with negative value

When setting a negative x, y value for transition, there’re following symptoms.
a. The contents of Dialog appear and disappear statically positioned*
b. Dialog’s size changes (e.g. onWidthChange is called ), 0 (when it’s hidden) to max width (when fully visible)
c. Slot onXChanged: is not called unless x value becomes positive.

*#1 can be improved by setting clip:true to Dialog.

How to reproduce
Run qtbug89135.zip