NPE for empty 'extensions' XML-document

[jenetics]

The following code will throw an NPE:

@Test
public void extensions() throws ParserConfigurationException {
	final DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
	final DocumentBuilder db = dbf.newDocumentBuilder();
	final Document doc = db.newDocument();

	GPX gpx = GPX.builder()
		.extensions(doc)
		.build();
}

java.lang.NullPointerException
	at io.jenetics.jpx.XML.checkExtensions(XML.java:281)
	at io.jenetics.jpx.GPX$Builder.extensions(GPX.java:759)
	at io.jenetics.jpx.GPXTest.extensions(GPXTest.java:75)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:124)
	at org.testng.internal.Invoker.invokeMethod(Invoker.java:583)
	at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:719)
	at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:989)
	at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
	at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
	at org.testng.TestRunner.privateRun(TestRunner.java:648)
	at org.testng.TestRunner.run(TestRunner.java:505)
	at org.testng.SuiteRunner.runTest(SuiteRunner.java:455)
	at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:450)
	at org.testng.SuiteRunner.privateRun(SuiteRunner.java:415)
	at org.testng.SuiteRunner.run(SuiteRunner.java:364)
	at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
	at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:84)
	at org.testng.TestNG.runSuitesSequentially(TestNG.java:1208)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1137)
	at org.testng.TestNG.runSuites(TestNG.java:1049)
	at org.testng.TestNG.run(TestNG.java:1017)
	at org.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:73)
	at org.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:123)

An IllegalArgumentException should be thrown instead.

[jenetics]

Merged into r1.5.3 branch.