NPE when using Phreak related to activation matches

Description of problem:
A problem occurs when switching from Rete to Phreak.
We get a NPE in the following code:
// @TODO (mdp) is this really necessary? won't the entire FH and RightTuple chaines just et GC'd?
unlinkCreatedHandles(leftTuple);

On line 268 : leftTuple.getObject

It seems like the 'match' is null at t+1 but it was not at t.

An extract of our rules is:
rule A
when
...
then
context.delete("D1");
end

rule B
when
Object(...) from context.get("D1")
then
...
end

Unfortunately, we haven't reproduced the bug yet in a unit test.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.
2.
3.

Actual results:

Expected results:

Additional info:
java.lang.NullPointerException
at org.drools.core.phreak.PhreakFromNode.unlinkCreatedHandles(PhreakFromNode.java:268)
at org.drools.core.phreak.PhreakFromNode.doLeftDeletes(PhreakFromNode.java:258)
at org.drools.core.phreak.PhreakFromNode.doNode(PhreakFromNode.java:41)
at org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:348)
at org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:162)
at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:117)
at org.drools.core.phreak.RuleExecutor.reEvaluateNetwork(RuleExecutor.java:199)
at org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:66)
at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:927)
at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1187)
at org.drools.core.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:957)
at org.drools.core.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:931)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:233)
at fr.edf.distribution.linky.lsp.DefaultTestWithSession.launchRules(DefaultTestWithSession.java:45)
at fr.edf.distribution.linky.lsp.TestRulesOnDysf.testRG_MO_02(TestRulesOnDysf.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:77)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:195)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:63)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)