Description of problem:

Can't debug drl if 'dialect "mvel"' in the rules.Below exception will occur:

java.lang.RuntimeException: no debugger registered to handle breakpoint
	at org.mvel2.debug.DebuggerContext.checkBreak(DebuggerContext.java:98)
	at org.mvel2.MVELRuntime.execute(MVELRuntime.java:76)
	at org.mvel2.compiler.CompiledExpression.getDirectValue(CompiledExpression.java:123)
	at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:119)
	at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:113)
	at org.mvel2.MVEL.executeExpression(MVEL.java:929)
	at org.drools.core.util.MVELSafeHelper$RawMVELEvaluator.executeExpression(MVELSafeHelper.java:496)
	at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:92)
	at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:77)
	at org.drools.core.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:248)
	at org.drools.core.rule.constraint.MvelConstraint.isAllowed(MvelConstraint.java:204)
	at org.drools.core.reteoo.AlphaNode.assertObject(AlphaNode.java:141)
	at org.drools.core.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:494)
	at org.drools.core.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:374)
	at org.drools.core.reteoo.ObjectTypeNode.propagateAssert(ObjectTypeNode.java:298)
	at org.drools.core.phreak.PropagationEntry$Insert.execute(PropagationEntry.java:93)
	at org.drools.core.phreak.SynchronizedPropagationList.flush(SynchronizedPropagationList.java:96)
	at org.drools.core.phreak.SynchronizedPropagationList.flush(SynchronizedPropagationList.java:69)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.flushPropagations(StatefulKnowledgeSessionImpl.java:1993)
	at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1289)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.internalFireAllRules(StatefulKnowledgeSessionImpl.java:1294)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1281)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1260)
	at com.sample.DroolsTest.main(DroolsTest.java:24)



Steps to Reproduce:
1.Create HelloWorld Drools example project in JBDS.
2.add dialect "mvel" for your rules and Set a breakpoint to the drl.
3.Debug As -> Drools Application

Actual results:
no debugger registered to handle breakpoint exception occur.

Expected results:
normally debug rules.

Additional info:
ENV:JDBS 9.0, Java 1.8, Windows 7/RHEL 7.2,  Drools 6.2 runtime

This issue has been reported to [1].

[1]https://issues.jboss.org/browse/DROOLS-785