Collection properties in builders are broken

The following markup fails to load in the most recent build:

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import javafx.scene.*?>
<?import javafx.scene.paint.*?>
<?import javafx.scene.shape.*?>

<Group xmlns:fx="http://javafx.com/fxml">
  <children>
    <Circle id="firstCircle" radius="10.0" fx:id="firstCircle">
      <fill>
        <LinearGradient endX="765.46" endY="196.48" proportional="false" startX="43.34" startY="196.48">
          <stops>
            <Stop>
              <color>
                <Color blue="0.384" green="0.027" red="0.031" fx:id="x2" />
              </color>
            </Stop>
            <Stop offset="1.0">
              <color>
                <Color blue="0.384" green="0.027" opacity="0.000" red="0.031" fx:id="x1" />
              </color>
            </Stop>
          </stops>
        </LinearGradient>
      </fill>
    </Circle>
    <Circle id="secondCircle" radius="10.0" fx:id="secondCircle">
      <fill>
        <LinearGradient endX="765.46" endY="196.48" proportional="false" startX="43.34" startY="196.48">
          <stops>
            <Stop color="$x1" />
            <Stop color="$x2" offset="1.0" />
          </stops>
        </LinearGradient>
      </fill>
    </Circle>
  </children>
</Group>