xml declaration is not followed by a newline

A DESCRIPTION OF THE PROBLEM :
Using LSSerializer to pretty-print a DOM results in an xml-declaration being not followed by a newline.

Related to bugs #7150637 and #8054115.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the following code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
<?xml version="1.0" encoding="UTF-8"?>
<sometag/>
ACTUAL -
<?xml version="1.0" encoding="UTF-8"?><sometag/>

---------- BEGIN SOURCE ----------
package io.github.oliviercailloux.jaris.xml;

import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSSerializer;

public class Snippet {
public static void main(String[] args) throws Exception {
final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
final DocumentBuilder builder = factory.newDocumentBuilder();
final Document document = builder.newDocument();

final Element child = document.createElement("sometag");
document.appendChild(child);

final DOMImplementationLS impl = (DOMImplementationLS) document.getImplementation().getFeature("LS", "3.0");
final LSSerializer ser = impl.createLSSerializer();
/** But see https://bugs.openjdk.java.net/browse/JDK-7150637 */
/**
* But see
* <a href="https://bugs.openjdk.java.net/browse/JDK-8054115">8054115</a>:
* LSSerializer remove a '\n' following the xml declaration
*/
ser.getDomConfig().setParameter("format-pretty-print", true);
final StringWriter writer = new StringWriter();
final LSOutput output = impl.createLSOutput();
output.setCharacterStream(writer);
ser.write(document, output);

System.out.println(writer.toString());
}
}

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FREQUENCY : always