Guarantee event's default state as not accepted

Before starting the evaluation of the event to check if it should be
accepted or not, set the state of the wheelEvent to not accepted. That
way, if the event is not accepted it will be propagated to others
elements.

Change-Id: I13a71db8e26c888adc03f1bfd3e46480d3b22b6f
Task-number: QTBUG-36774
Reviewed-by: Gustavo Pichorim Boiko <gustavo.boiko@canonical.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Do not add Images with invalid geometry to the scene graph.

Task-number: QTBUG-35656
Task-number: QTBUG-36050

Change-Id: Iea2d5303bdeb9c523e59ebcdc9f97288060be022
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>