hg: jigsaw/jake/jdk: Change default module version from "" to null.

[harold.seigel at oracle.com]

Changeset: 7919272336c9
Author:    hseigel
Date:      2015-10-23 12:27 -0400
URL:       http://hg.openjdk.java.net/jigsaw/jake/jdk/rev/7919272336c9

Change default module version from "" to null.

! src/java.base/share/classes/java/lang/reflect/Module.java