Hi Martin,
Good findings.
I skipped the instructions to delete ejbModule/META-INF/openejb-jar.xml during my testing so it worked well. If I delete this file I can reproduce your exception in my environment.
I opened two JIRAs.
1. https://issues.apache.org/jira/browse/GERONIMODEVTOOLS-689 NullPointerException when publishing with Geronimo Eclipse Plugin v2.1.7 (I think it needs either code or document update or even both)
2. https://issues.apache.org/jira/browse/GERONIMODEVTOOLS-690 NullpointerException occurs if one adds a "Utility Project" to the EAR
Thanks very much for catching the problem.
Best regards,

Han Hong Fang (Janet)
hanhongfang AT apache.org