MuonD3PDMaker: Create MCTruthClassifier cache.

    
Create MCTruthClassifier cache where needed.
Fixes crashes observed in master.

PhysicsAnalysis/D3PDMaker/MuonD3PDMaker/src/MuonGenParticleAssociationTool.cxx

@@ -75,7 +75,9 @@ StatusCode MuonGenParticleAssociationTool::book ()
 const xAOD::TruthParticle*
 MuonGenParticleAssociationTool::get (const xAOD::Muon& p)
 {
+  IMCTruthClassifier::Cache cache;
   IMCTruthClassifier::Info info;
+  info.extrapolationCache = &cache;
   const xAOD::TruthParticle* out = 0;
   if (m_classifier->particleTruthClassifier (&p, &info).first !=
       MCTruthPartClassifier::Unknown)