In some instances, a NullPointerException is thrown while running the unpack command.
The pack command used to populate the jar file did not complete successfully. For example, if the pack command were run while the admin and/or managed servers of the domain were still running, the pack command would not be able to complete, and the jar file it builds would not be complete either. Then if the same incomplete jar file is used for the unpack command, it will lack some of what it needs, and the error will occur.
Make sure that the pack command has completed before taking the jar file and using it for unpack. In the example, make sure that the admin and managed servers of a domain have been shut down before running the pack command so that it can complete. After it has completed, the jar file will be usable and then it can be used to unpack.