[C++] Initialize inertia, jointPlacements and parent of universe joint in Model

src/multibody/model.hpp

@@ -115,10 +115,10 @@ namespace se3
       , njoint(1)
       , nbody(1)
       , nFrames(0)
-      , inertias(1)
-      , jointPlacements(1)
+      , inertias(1, Inertia::Zero())
+      , jointPlacements(1, SE3::Identity())
       , joints(1)
-      , parents(1)
+      , parents(1, 0)
       , names(1)
       , subtrees(1)
       , gravity( gravity981,Eigen::Vector3d::Zero() )