ComboBox: Fix selected item alignment
ComboBox: Fix selected item alignment

We seem to receive a size change later that we used to, and this exposed
a bug were the popup would always be aligned on the first item.

Change-Id: I7b7b4ca5fcff969c3b492419cab7447170a2c3f5
Reviewed-by: J-P Nurmi <b84a892f57a298bb5dae653b4e188948a84d5549@digia.com>

drgvond/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,kobolabs/qtquickcontrols,mizukusak/qtquickcontrols,kobolabs/qtquickcontrols,kobolabs/qtquickcontrols,drgvond/qtquickcontrols