javax.lang.model.element.ModuleElement.getDirectives() causes NPE if corresponding ModuleElement instance represents unnamed module.

The minimized testcase is attached. In order to reproduce it, please:
1. Unzip attached archive on some Unix/Linux machine to a directory, say A.
2. Modify A/Test21/test.sh by setting JDK_HOME environment variable to your JDK installation.
3. Run A/Test21/test.sh.

On JDK9b125 this causes following output:

Root elements number: 1

Root class: Test21
Package: unnamed package
Module: unnamed module
Invoking getDirectives():


An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.NullPointerException
        at java.util.Collections$UnmodifiableCollection.<init>(java.base@9-ea/Collections.java:1027)
        at java.util.Collections$UnmodifiableList.<init>(java.base@9-ea/Collections.java:1303)
        at java.util.Collections.unmodifiableList(java.base@9-ea/Collections.java:1290)
        at com.sun.tools.javac.code.Symbol$ModuleSymbol.getDirectives(jdk.compiler@9-ea/Symbol.java:937)
        at Test21Proc.process(Test21Proc.java:22)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(jdk.compiler@9-ea/JavacProcessingEnvironment.java:961)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(jdk.compiler@9-ea/JavacProcessingEnvironment.java:877)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$2100(jdk.compiler@9-ea/JavacProcessingEnvironment.java:107)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1184)
        at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(jdk.compiler@9-ea/JavacProcessingEnvironment.java:1292)
        at com.sun.tools.javac.main.JavaCompiler.processAnnotations(jdk.compiler@9-ea/JavaCompiler.java:1229)
        at com.sun.tools.javac.main.JavaCompiler.compile(jdk.compiler@9-ea/JavaCompiler.java:903)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:280)
        at com.sun.tools.javac.main.Main.compile(jdk.compiler@9-ea/Main.java:144)
        at com.sun.tools.javac.Main.compile(jdk.compiler@9-ea/Main.java:55)
        at com.sun.tools.javac.Main.main(jdk.compiler@9-ea/Main.java:41)