Fix crash issue when SetProperty is called with an invalid type

Previously this would result in a crash, since the PropertyMetadata
would be overwritten with the incorrect type of Property::Value

    float uRadius( 5.0f );
    actor.RegisterProperty( "radius", uRadius );

    Property::Value propertyValue;
    propertyValue = int(1);

    Property::Index radius = actor.GetPropertyIndex( "radius" );
    actor.SetProperty( radius, propertyValue );

The crash happens after attempting to cast to the wrong type of
AnimatableProperty in Actor::SetSceneGraphProperty

Change-Id: I8d42d190f81ff97cb9667da248911ed5ae6475dc