Fix bounding box assertions due to negative particle life time

Other parts of the code could not deal with negative life times and produced negative particle sizes as a result (which Ogre could not handle)

components/nifogre/ogrenifloader.cpp

@@ -749,8 +749,8 @@ class NIFObjectLoader
         emitter->setParticleVelocity(partctrl->velocity - partctrl->velocityRandom*0.5f,
                                      partctrl->velocity + partctrl->velocityRandom*0.5f);
         emitter->setEmissionRate(partctrl->emitRate);
-        emitter->setTimeToLive(partctrl->lifetime - partctrl->lifetimeRandom*0.5f,
-                               partctrl->lifetime + partctrl->lifetimeRandom*0.5f);
+        emitter->setTimeToLive(partctrl->lifetime,
+                               partctrl->lifetime + partctrl->lifetimeRandom);
         emitter->setParameter("width", Ogre::StringConverter::toString(partctrl->offsetRandom.x));
         emitter->setParameter("height", Ogre::StringConverter::toString(partctrl->offsetRandom.y));
         emitter->setParameter("depth", Ogre::StringConverter::toString(partctrl->offsetRandom.z));