Interested in an NPE ?
5.5.0.Final
in class NamedEntryPoint :

    protected FactHandle insert(final Object object,
                                final Object tmsValue,
                                final boolean dynamic,
                                boolean logical,
                                final Rule rule,
                                final Activation activation) throws FactException {
        if ( object == null ) {
            // you cannot assert a null object
            return null;
        }

        try {
            this.wm.startOperation();

            ObjectTypeConf typeConf = this.typeConfReg.getObjectTypeConf( this.entryPoint,
                                                                          object );
            if ( logical && !typeConf.isTMSEnabled()) {
                enableTMS(object, typeConf);
            }

            InternalFactHandle handle = null;

            if ( this.wm.isSequential() ) {
                handle = createHandle( object,
                                       typeConf );
                insert( handle,
                        object,
                        rule,
                        activation,
                        typeConf );
                return handle;
            }
            try {
                this.lock.lock();
                this.ruleBase.readLock();
                // check if the object already exists in the WM
                handle = this.objectStore.getHandleForObject( object );

                if ( typeConf.isTMSEnabled() ) {

                    EqualityKey key;

                    TruthMaintenanceSystem tms = wm.getTruthMaintenanceSystem();
                    if ( handle == null ) {
                        // lets see if the object is already logical asserted
                        key = tms.get( object );
                    } else {
                        // Object is already asserted, so check and possibly correct its
                        // status and then return the handle
                        key = handle.getEqualityKey();

                        if ( key.getStatus() == EqualityKey.STATED ) {

// key == null here !!!!!!!!!!!!!!!!!!!
//  conf.setAssertBehaviour( AssertBehaviour.EQUALITY );

// inserting Triple :
<file:/home/jmv/src/eulergui-code/eulergui/test/import.n3p.n3> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Ontology> .

that is already present.

And the rule is :
// ---------- N3 rule 9 ----------
/* {
?ONTO <http://www.w3.org/2002/07/owl#imports> ?X.
}
 => {
?ONTO <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Ontology>.
}. */

rule "project-java-rules.n3 9"
when
  $Triple_1 : Triple( $ONTO : subject, predicate == "<http://www.w3.org/2002/07/owl#imports>", $X : object )
then
  Triple newTriple;
  TripleResult newTripleResult;
  newTriple = new Triple(  );
  newTriple.setSubject( $ONTO );
  newTriple.setPredicate( "<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>".toString() );
  newTriple.setObject( "<http://www.w3.org/2002/07/owl#Ontology>" );  insertLogical( newTriple );
end