Proper error message should be raised in case versioining is not properly defined against the given jar when "arvhive_x" attribute is used. This will help developers in debugging the issue promptly as under some scenarios raised exception seems to irrelevant.

Steps to reproduce:
-------------------
1) Try to Load the following applet
http://nicole1.sfbay.sun.com:8080/jnlpstyle/tests/negative/TestCacheVersionarchive_x.html
Here versioning is missing against the following jars at server end
<param name=archive_2 value=MazeUtil1.jar,version=1.0*>
<param name=archive_3 value=MazeUtil2.jar,version=1.0+>

Applet as of now failing to load by throwing followig error message and by reading this message one cannot make out that in fact there is something wrong with jar versioing:
java.lang.NullPointerException
at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NullPointerException