Drop a Button
From the inspector, click in the style property first TextField, and enter 'fill'
Select '-fx-text-fill'
The following NPE is raised:

java.lang.NullPointerException
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.editors.StyleEditor$StyleItem.getValue(StyleEditor.java:330)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.editors.StyleEditor$StyleItem.lambda$0(StyleEditor.java:256)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.editors.StyleEditor$StyleItem$$Lambda$563/1310439762.handle(Unknown Source)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.InspectorPanelController.lambda$8(InspectorPanelController.java:1178)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.InspectorPanelController$$Lambda$539/1925236360.changed(Unknown Source)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:182)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.BooleanPropertyBase.fireValueChangedEvent(BooleanPropertyBase.java:103)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.beans.property.BooleanProperty.setValue(BooleanProperty.java:77)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.editors.InlineListEditor.editing(InlineListEditor.java:90)
at com.oracle.javafx.scenebuilder.kit.editor.panel.inspector.editors.StyleEditor$StyleItem.lambda$2(StyleEditor.java:293)