[jdom-interest] Bug in XMLOutputter or Element.addAttribute depending on whether null is valid

[Scott M Stark]

The Element class allows one to add an attribute with a null value. However, when you
try to output such an element with the XMLOutputter it crashes because it does not
protect against attributes having null values. This is with the jdom b5 release.

bash-2.04$ cat tstOut.java
import java.io.*;
import org.jdom.*;
import org.jdom.output.*;

class tstOut
{
        public static void main(String[] args) throws Exception
        {
                Element root = new Element("ProjectInfo");
                root.addAttribute("name", "project1");
                root.addAttribute("description", null);
                Document doc = new Document(root);
                XMLOutputter output = new XMLOutputter("  ");
                output.output(doc, new FileOutputStream("out.xml"));
        }
}
bash-2.04$ java -classpath ".;build/jdom.jar" tstOut
Exception in thread "main" java.lang.NullPointerException
        at org.jdom.output.XMLOutputter.escapeAttributeEntities(XMLOutputter.java:1143)
        at org.jdom.output.XMLOutputter.printAttributes(XMLOutputter.java:1125)
        at org.jdom.output.XMLOutputter.printElement(XMLOutputter.java:907)
        at org.jdom.output.XMLOutputter.output(XMLOutputter.java:522)
        at org.jdom.output.XMLOutputter.output(XMLOutputter.java:494)
        at org.jdom.output.XMLOutputter.output(XMLOutputter.java:453)
        at tstOut.main(tstOut.java:14)
bash-2.04$