Fix Pythia::init call.

Pythia8Generator.cpp

@@ -145,7 +145,9 @@ public:
             getOption("colliding particle 1",coll_particle1);
             getOption("colliding particle 2",coll_particle2);
             getOption("center mass energy",cme);
-            pythia8.init(getParticleId(coll_particle1.back()), getParticleId(coll_particle2.back()), cme);
+            pythia8.init();
+            pythia8.setBeamIDs(getParticleId(coll_particle1.back()), getParticleId(coll_particle2.back()));
+            pythia8.setKinematics(cme);
             getOption("stored particles",mode);
             storedParticles=getStoredParticles(mode.back());
         }