Boolean config values that are not declared explicitly currently default to NULL, resulting in NPE's.

ex.
in sp-metadata.xml, SPSSODescriptor element:
AuthnRequestsSigned="false" WantAssertionsSigned="true"

if you don't specify these attributes, you will get a failed trust relationship with the SP after authing:

2014-02-27 09:12:11,335 ERROR [org.picketlink.identity.federation] (http-/10.25.103.104:8080-1) PLFED000253: Exception in processing request: java.lang.NullPointerException
at org.picketlink.identity.federation.bindings.tomcat.idp.AbstractIDPValve.willIgnoreSignatureOfCurrentRequest(AbstractIDPValve.java:1431) [picketlink-jbas7.jar:2.1.9.SP2]
at org.picketlink.identity.federation.bindings.tomcat.idp.AbstractIDPValve.processSAMLRequestMessage(AbstractIDPValve.java:685) [picketlink-jbas7.jar:2.1.9.SP2]
at org.picketlink.identity.federation.bindings.tomcat.idp.AbstractIDPValve.handleSAMLMessage(AbstractIDPValve.java:329) [picketlink-jbas7.jar:2.1.9.SP2]
at org.picketlink.identity.federation.bindings.tomcat.idp.AbstractIDPValve.invoke(AbstractIDPValve.java:284) [picketlink-jbas7.jar:2.1.9.SP2]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169) [jboss-as-web.jar:7.3.1.Final-redhat-4]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:145) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.jboss.as.web.sso.ClusteredSingleSignOn.invoke(ClusteredSingleSignOn.java:384) [jboss-as-web.jar:7.3.1.Final-redhat-4]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:336) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653) [jbossweb.jar:7.3.0.Final-redhat-1]
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:920) [jbossweb.jar:7.3.0.Final-redhat-1]
at java.lang.Thread.run(Thread.java:744) [rt.jar:1.7.0_51]