Fix Slider regression
Fix Slider regression

The change in implicit size means that by default the size is not
0. Since the slider was creating a hidden slider item, we have to
hide this explicitly.

Change-Id: I5342376ab209409a580b9380deff6f53b0d94f63
Reviewed-by: Daker Fernandes Pinheiro <7c8be063491dd997a6f8c774cf795e75384ede54@openbossa.org>
Reviewed-by: Jens Bache-Wiig <9cea9d70b08f8210134ec5959114f72bad51ed1d@nokia.com>

jfaust/qtquickcontrols,jfaust/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,richardmg/qtcomponents,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,richardmg/qtcomponents,jfaust/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,drgvond/qtquickcontrols,richardmg/qtcomponents