plot points fill property should take scalar

[scottdraves]

def plot = new Plot(title: "Changing Point Size, Color")
def y1 = [6, 7, 12, 11, 8, 14]
def y2 = y1.collect { it - 2 }
def y3 = y2.collect { it - 2 }
def y4 = y3.collect { it - 2 }
plot << new Points(y: y1)
plot << new Points(y: y2, size: 10, color: Color.black)
plot << new Points(y: y3, size: 15, color: Color.orange, outlineColor: Color.black)
plot << new Points(y: y4, size: 20, outlineColor: Color.red, fill: false)

this should not crash.