Fix ghost replay crashes

src/karts/kart.cpp

@@ -858,6 +858,8 @@ void Kart::adjustSpeed(float f)
  */
 void Kart::updateWeight()
 {
+    if (!m_body)
+        return;
     float mass = m_kart_properties->getMass() + m_attachment->weightAdjust();
     if (m_weight != mass)
     {

src/karts/moveable.cpp

@@ -62,7 +62,10 @@ void Moveable::setNode(scene::ISceneNode *n)
 //-----------------------------------------------------------------------------
 void Moveable::updateSmoothedGraphics(float dt)
 {
-    SmoothNetworkBody::updateSmoothedGraphics(m_transform, getVelocity(), dt);
+    Vec3 velocity;
+    if (m_body)
+        velocity = m_body->getLinearVelocity();
+    SmoothNetworkBody::updateSmoothedGraphics(m_transform, velocity, dt);
 #undef DEBUG_SMOOTHING
 #ifdef DEBUG_SMOOTHING
     // Gnuplot compare command