The following test fails with

java.lang.IndexOutOfBoundsException: index=3
at jfx.incubator.richtext/jfx.incubator.scene.control.richtext.RichTextArea.getPlainText(RichTextArea.java:1494)
at jfx.incubator.richtext/jfx.incubator.scene.control.richtext.RichTextArea.getText(RichTextArea.java:1552)
at jfx.incubator.richtext/jfx.incubator.scene.control.richtext.RichTextArea$1.getText(RichTextArea.java:322)
at jfx.incubator.richtext/com.sun.jfx.incubator.scene.control.richtext.RichTextAreaHelper.getText(RichTextAreaHelper.java:59)
at jfx.incubator.richtext/test.jfx.incubator.scene.control.richtext.CodeAreaTest.selectAll(CodeAreaTest.java:327)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1604)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1604)




```
    @Test
    public void selectAll() {
        String text =
            """
            Hello, Javafx1
            Hello, Javafx2
            """;
        control.setText(text);
        assertEquals(3, control.getParagraphCount());

        control.selectAll();
        SelectionSegment sel = control.getSelection();
        StringBuilder sb = new StringBuilder();
        RichTextAreaHelper.getText(control, sel.getMin(), sel.getMax(), sb, Integer.MAX_VALUE);
        assertEquals(text, sb.toString());
    }
```

The same issue is present in RichTextArea.

Thanks to https://github.com/oyzh1994 for discovering the bug and providing a test case: https://github.com/andy-goryachev-oracle/Test/issues/6#issuecomment-3726867016