joint/ff: fix bug

src/multibody/joint/joint-free-flyer.hpp

@@ -192,7 +192,7 @@ namespace pinocchio
     : M(1)
     , U(U_t::Zero())
     , Dinv(D_t::Zero())
-    , UDinv(UD_t::Zero())
+    , UDinv(UD_t::Identity())
     {}
 
     static std::string classname() { return std::string("JointDataFreeFlyer"); }