update Positioner::syncGeometry in specific case

--when a behaveAsPlasmaPanel is sliding-in and View
is in editMode, it is a good idea to calle
Positioner::syncGeometry() in order to validate
the View window geometry in edit mode. The problematic
case example was a right SideBar Panel that when
was hidden and the user was using Meta+A to
show its settings, the View did not change its
geometry properly in the end.