[rules-users] NullPointerException during removing knowledge packages

[Piotr Jedrychowski]

Hello.

I have a problem with removing knowledge packages. During running this 
source code
Collection<KnowledgePackage> knowledgePackages = 
knowledgeBase.getKnowledgePackages();
if (knowledgePackages != null) {
     List<String> packageNames = new ArrayList<String>();
     for (KnowledgePackage singlePackage : knowledgePackages) {
         packageNames.add(singlePackage.getName());
     }

     for (String singlePackageName : packageNames) {
         knowledgeBase.removeKnowledgePackage(singlePackageName);
     }
}

I'm getting NullPointerException with this StackTrace:
java.lang.NullPointerException
  at org.drools.reteoo.ReteooBuilder.removeRule(ReteooBuilder.java:235)
  at org.drools.reteoo.ReteooRuleBase.removeRule(ReteooRuleBase.java:366)
  at 
org.drools.common.AbstractRuleBase.removeRule(AbstractRuleBase.java:712)
  at 
org.drools.common.AbstractRuleBase.removePackage(AbstractRuleBase.java:640)
  at 
org.drools.impl.KnowledgeBaseImpl.removeKnowledgePackage(KnowledgeBaseImpl.java:166)

I found this links in Internet:
http://seamframework.org/Community/DroolsGuvnorCacheIssue
http://lists.jboss.org/pipermail/rules-users/2007-November/003917.html

Maybe someone had similar problem and could help me?

I'm using:
* JBoss 4.2.3.GA
* Drools 5.0

Regards,
Piotr