NPE when calling removeRule in Drools - drools

Question

When I use the API KnowledgeBaseImpl.removeRule() in Drools 7.56.0.Final, NPE was thrown.
We use template to create rule, the content is like:
package drools.template;\nimport java.text.SimpleDateFormat;\nimport java.util.Date;\n\nrule "651657095963213824-651657096034516992"\n when\n $p: com.seewo.ucp.hub.domain.strategy.aggregation.StrategyRule((deviceDto.lamp == com.seewo.ucp.hub.domain.device.enums.DeviceEventTypeEnum.ONLINE) && (date ==1628645220445))\n then\n $p.setResult(Boolean.TRUE);\nend\n\n\n
The add rule code:
KnowledgeBuilder knowledgeBuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
knowledgeBuilder.add(ResourceFactory.newByteArrayResource(drlContent.getBytes(StandardCharsets.UTF_8)), ResourceType.DRL);
if (knowledgeBuilder.hasErrors()) {
return;
}
((KnowledgeBaseImpl) kieBase).addPackages(knowledgeBuilder.getKnowledgePackages());
The remove rule code:
if (isRuleExist(ruleName)) {
kieBase.removeRule(packageName, ruleName);
}
Here, isRuleExist() is a function to check if the rule exists or not: kieBase.getRule(packageName, ruleName) != null.
When I removed the rule, NPE thrown:
java.lang.NullPointerException: null
at org.drools.core.phreak.AddRemoveRule.iterateLeftTuple(AddRemoveRule.java:1081) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.phreak.AddRemoveRule.visitChild(AddRemoveRule.java:996) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.phreak.AddRemoveRule.lambda$processLeftTuplesOnLian$1(AddRemoveRule.java:954) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.common.DefaultFactHandle$SingleLinkedTuples.forEachLeftTuple(DefaultFactHandle.java:739) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.common.DefaultFactHandle.forEachLeftTuple(DefaultFactHandle.java:935) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.phreak.AddRemoveRule.processLeftTuplesOnLian(AddRemoveRule.java:949) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.phreak.AddRemoveRule.processLeftTuples(AddRemoveRule.java:870) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.phreak.AddRemoveRule.removeRule(AddRemoveRule.java:179) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.reteoo.ReteooBuilder.removeTerminalNode(ReteooBuilder.java:191) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.reteoo.ReteooBuilder.removeRules(ReteooBuilder.java:177) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.impl.KnowledgeBaseImpl.lambda$removeRule$6(KnowledgeBaseImpl.java:1559) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.impl.KnowledgeBaseImpl.enqueueModification(KnowledgeBaseImpl.java:748) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
at org.drools.core.impl.KnowledgeBaseImpl.removeRule(KnowledgeBaseImpl.java:1543) ~[drools-core-7.56.0.Final.jar:7.56.0.Final]
any help is appreciated