ExtensionIndexService throws NPE while reading extensions on the IBM jdk

https://github.com/wildfly/wildfly-core/blob/5.0.0.Alpha7/server/src/main/java/org/jboss/as/server/moduleservice/ExtensionIndexService.java#L94 reads extensions from jars manifest like:

File jar = new File(<jar>)
final JarFile jarFile = new JarFile(jar);
final Manifest manifest = jarFile.getManifest();
final Attributes mainAttributes = manifest.getMainAttributes();
...

The latest IBM jdk 8.0-5.11 (and possible some of previous releases) contains some jars [1] where manifest.getMainAttributes(); throws NPE, causing deploy operation of archive with Extension-List to fail, see WFLY-10349.

[1]
ibm-java-8.0-5.11/jre/lib/ext/traceformat.jar: java.lang.NullPointerException
ibm-java-8.0-5.11/jre/lib/ext/dtfj.jar: java.lang.NullPointerException
ibm-java-8.0-5.11/jre/lib/ext/dtfjview.jar: java.lang.NullPointerException