[MNG-8369] Empty .mvn/extensions.xml should not just print EOFException

**[Benjamin Marwell](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mampf86)** opened **[MNG-8369](https://issues.apache.org/jira/browse/MNG-8369?redirect=false)** and commented

`{}touch{`}ing an empty file `.mvn/extensions.xml` will lead to:

```
+ ./mvnw --no-transfer-progress verify
Apache Maven 3.9.9 (8e8579a9e76f7d015ee5ec7bfcdc97d260186937)
Maven home: /home/user/.m2/wrapper/dists/apache-maven-3.9.9/490815c6
Java version: 21.0.4, vendor: IBM Corporation, runtime: /home/user/jenkins/tools/hudson.model.JDK/jdk21
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "5.14.21-150500.55.68-default", arch: "amd64", family: "unix"
[ERROR] Error executing Maven.
java.io.EOFException: input contained no data
at org.codehaus.plexus.util.xml.pull.MXParser.fillBuf (MXParser.java:3898)
at org.codehaus.plexus.util.xml.pull.MXParser.more (MXParser.java:3980)
at org.codehaus.plexus.util.xml.pull.MXParser.parseProlog (MXParser.java:1774)
at org.codehaus.plexus.util.xml.pull.MXParser.nextImpl (MXParser.java:1757)
at org.codehaus.plexus.util.xml.pull.MXParser.next (MXParser.java:1375)
at org.apache.maven.cli.internal.extension.model.io.xpp3.CoreExtensionsXpp3Reader.read (CoreExtensionsXpp3Reader.java:586)
at org.apache.maven.cli.internal.extension.model.io.xpp3.CoreExtensionsXpp3Reader.read (CoreExtensionsXpp3Reader.java:613)
at org.apache.maven.cli.internal.extension.model.io.xpp3.CoreExtensionsXpp3Reader.read (CoreExtensionsXpp3Reader.java:628)
at org.apache.maven.cli.internal.extension.model.io.xpp3.CoreExtensionsXpp3Reader.read (CoreExtensionsXpp3Reader.java:659)
at org.apache.maven.cli.MavenCli.readCoreExtensionsDescriptor (MavenCli.java:770)
at org.apache.maven.cli.MavenCli.loadCoreExtensions (MavenCli.java:713)
at org.apache.maven.cli.MavenCli.container (MavenCli.java:627)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:277)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:206)
at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:103)
at java.lang.reflect.Method.invoke (Method.java:586)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:255)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:201)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:361)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:314)
```

---

**Affects:** 3.9.9