Running the example below fails with the stacktrace (excerpt)

Caused by: java.lang.NullPointerException
at javafx.scene.control.TextInputControl.updateText(TextInputControl.java:1218)
at javafx.scene.control.TextInputControl.access$300(TextInputControl.java:79)
at javafx.scene.control.TextInputControl$5.invalidated(TextInputControl.java:320)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:147)
at javafx.scene.control.TextInputControl.setTextFormatter(TextInputControl.java:334)

The technical reason seems to be the defaultConverter installed by CellUtils - its toString returns a null if the input param is null. That differs from all (?) other StringConverters in core which return an empty string.

Not sure who's the culprit: on the one hand, null behaviour/return value in StringConverter is not specified, on the other hand TextProperty usually takes care of passing a null as empty string to Content - but replace doesn't.

The example:
public class ComboBoxTableCellConverterAndTextFormatter extends Application {

    private Parent getContent() {
        TextField field = new TextField("some dummy");
        TextFormatter formatter = new TextFormatter(new ComboBoxTableCell().getConverter());
        // the default in TextFormatter is okay
        //TextFormatter formatter = new TextFormatter(TextFormatter.IDENTITY_STRING_CONVERTER);
        field.setTextFormatter(formatter);
        return field;
    }
    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setScene(new Scene(getContent()));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
    
}