Salience format error not directly noticed by Eclipse plugin or at compile time

rule "If no existing wrapper make one"
no-loop
salience - 50 //Error in formatting - space between - and 50 not compile time or Eclipse editor error
	when
	   $tp : TextPosition($textStart : indexstart, $textEnd : indexend, $text : text, $metrics : Metrics, !discard)
	   FormatWrapper($formatStart: format.startPos, $formatEnd: format.endPos)
	   eval($textStart >= $formatStart || $textEnd >= $formatStart) //Check for overlap
	   eval($formatStart >= $textStart || $formatEnd >= $textStart)
	   not TextWrapper(texpos == $tp)
	then
		TextWrapper tw = new TextWrapper($text,$metrics,$tp);
		insert(tw);				
end

Exception executing consequence for rule "Wrap FormatData" in guessing: java.lang.NullPointerException
	at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101)
	at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029)
	at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1251)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:709)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:673)
	at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:219)
	at drools.PhraseAnalyse.analyseTitle(PhraseAnalyse.java:39)
	at pdfbox.maintest.main(maintest.java:43)
Caused by: java.lang.NullPointerException
	at org.drools.base.mvel.MVELSalienceExpression.getValue(MVELSalienceExpression.java:86)
	at org.drools.reteoo.RuleTerminalNode.createActivations(RuleTerminalNode.java:279)
	at org.drools.reteoo.RuleTerminalNode.assertLeftTuple(RuleTerminalNode.java:184)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:197)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:86)
	at org.drools.reteoo.NotNode.assertLeftTuple(NotNode.java:100)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:197)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:86)
	at org.drools.reteoo.EvalConditionNode.assertLeftTuple(EvalConditionNode.java:183)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:197)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:86)
	at org.drools.reteoo.EvalConditionNode.assertLeftTuple(EvalConditionNode.java:183)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:197)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:72)
	at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:161)
	at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:458)
	at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:386)
	at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:211)
	at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:244)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:336)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:297)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:887)
	at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:180)
	at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:174)
	at guessing.Rule_Wrap_FormatData_55c760725b024ac8b9db87cf6c1aaa5c.defaultConsequence(Rule_Wrap_FormatData_55c760725b024ac8b9db87cf6c1aaa5c.java:9)
	at guessing.Rule_Wrap_FormatData_55c760725b024ac8b9db87cf6c1aaa5cDefaultConsequenceInvokerGenerated.evaluate(Unknown Source)
	at guessing.Rule_Wrap_FormatData_55c760725b024ac8b9db87cf6c1aaa5cDefaultConsequenceInvoker.evaluate(Unknown Source)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091)
	... 7 more