Trying to run any JavaFX application on Linux with prism.useFontConfig=false, fails with a NPE happening in LogicalFont:

Caused by: java.lang.NullPointerException: Cannot read field "firstFont" because "<local4>" is null
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.<init>(LogicalFont.java:177)
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.getLogicalFont(LogicalFont.java:109)
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.getLogicalFont(LogicalFont.java:149)
        at javafx.graphics@23-ea/com.sun.javafx.font.PrismFontFactory.createFont(PrismFontFactory.java:636)
        at javafx.graphics@23-ea/com.sun.javafx.font.PrismFontLoader.loadFont(PrismFontLoader.java:223)
        at javafx.graphics@23-ea/javafx.scene.text.Font.<init>(Font.java:346)
        at javafx.graphics@23-ea/javafx.scene.text.Font.getDefault(Font.java:110)
        at javafx.graphics@23-ea/javafx.scene.CssStyleHelper.<clinit>(CssStyleHelper.java:1695)
        ... 20 more

The following simple test can be used to reproduce the issue:

public class HelloFX extends Application {

    public void start(Stage stage) {
        Scene scene = new Scene(new StackPane());
        stage.setScene(scene);
        stage.show();
    }
}

Run it with -Dprism.useFontConfig=false and it will show this fatal exception (the application doesn't show up, the process ends):

Error: JavaFX detected no fonts! Please refer to release notes for proper font configuration
Exception in Application start method
java.lang.reflect.InvocationTargetException
        at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:118)
        at java.base/java.lang.reflect.Method.invoke(Method.java:580)
        at javafx.graphics@23-ea/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
        at javafx.graphics@23-ea/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:364)
        at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
        at java.base/java.lang.reflect.Method.invoke(Method.java:580)
        at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1135)
Caused by: java.lang.RuntimeException: Exception in Application start method
        at javafx.graphics@23-ea/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:893)
        at javafx.graphics@23-ea/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
        at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.ExceptionInInitializerError
        at javafx.graphics@23-ea/javafx.scene.Node.reapplyCss(Node.java:9524)
        at javafx.graphics@23-ea/javafx.scene.Node.reapplyCSS(Node.java:9487)
        at javafx.graphics@23-ea/javafx.scene.Node.invalidatedScenes(Node.java:1071)
        at javafx.graphics@23-ea/javafx.scene.Node.setScenes(Node.java:1136)
        at javafx.graphics@23-ea/javafx.scene.Scene$8.invalidated(Scene.java:1246)
        at javafx.base@23-ea/javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
        at javafx.base@23-ea/javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:147)
        at javafx.graphics@23-ea/javafx.scene.Scene.setRoot(Scene.java:1198)
        at javafx.graphics@23-ea/javafx.scene.Scene.<init>(Scene.java:362)
        at javafx.graphics@23-ea/javafx.scene.Scene.<init>(Scene.java:213)
        at hellofx.HelloFX.start(HelloFX.java:53)
        at javafx.graphics@23-ea/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:839)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:483)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:456)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:455)
        at javafx.graphics@23-ea/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
        at javafx.graphics@23-ea/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
        at javafx.graphics@23-ea/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$10(GtkApplication.java:264)
        ... 1 more
Caused by: java.lang.NullPointerException: Cannot read field "firstFont" because "<local4>" is null
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.<init>(LogicalFont.java:177)
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.getLogicalFont(LogicalFont.java:109)
        at javafx.graphics@23-ea/com.sun.javafx.font.LogicalFont.getLogicalFont(LogicalFont.java:149)
        at javafx.graphics@23-ea/com.sun.javafx.font.PrismFontFactory.createFont(PrismFontFactory.java:636)
        at javafx.graphics@23-ea/com.sun.javafx.font.PrismFontLoader.loadFont(PrismFontLoader.java:223)
        at javafx.graphics@23-ea/javafx.scene.text.Font.<init>(Font.java:346)
        at javafx.graphics@23-ea/javafx.scene.text.Font.getDefault(Font.java:110)
        at javafx.graphics@23-ea/javafx.scene.CssStyleHelper.<clinit>(CssStyleHelper.java:1692)
        ... 20 more
Exception running application hellofx.HelloFX

It can be reproduced with any JavaFX version on Linux (I am using Ubuntu 22.04.4).

Related: When running on Android (after JDK-8246104), with the same system property, the exception happens in FTFactory:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.font.FontConfigManager.getFileNames(FontConfigManager.java:314)
at com.sun.javafx.font.freetype.FTFactory.getFallbacks(FTFactory.java:136)
at com.sun.javafx.font.LogicalFont.getLinkedFonts(LogicalFont.java:214)
at com.sun.javafx.font.LogicalFont.getNumSlots(LogicalFont.java:223)
at com.sun.javafx.font.CompositeGlyphMapper.<init>(CompositeGlyphMapper.java:62)
at com.sun.javafx.font.LogicalFont.getGlyphMapper(LogicalFont.java:440)
at com.sun.javafx.text.PrismTextLayout.shape(PrismTextLayout.java:917)

In both cases (LogicalFont and FTFactory), there is a call to FontConfigManager.getFontConfigFont, but then there is no null check, for the possible cases where it might return null.