Use QMetaType::Float as this is what type() returns now

QVariant::Type is obsolete and type() is really returning a
QMetaType::Type instead. So for the float case we just add that in to
ensure it works as before in Qt 4.x.

Change-Id: I190a4eb2c37492386ea202fc52d39b431e5f02ff
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>