Roll back recent change to mjData.qLD until some issues are resolved.

PiperOrigin-RevId: 724389161
Change-Id: I1b30ab0950ab5c5e611b1c6fc3bf3f42f964939c

src/engine/engine_vis_interact.c

@@ -556,8 +556,7 @@ void mjv_initPerturb(const mjModel* m, mjData* d, const mjvScene* scn, mjvPertur
 
   // compute average spatial inertia at selection point
   for (int i=0; i < nv; i++) {
-    int diag = d->C_rowadr[i] + d->C_rownnz[i] - 1;
-    sqrtInvD[i] = 1 / mju_sqrt(d->qLD[diag]);
+    sqrtInvD[i] = 1 / mju_sqrt(d->qLD[m->dof_Madr[i]]);
   }
   mj_jac(m, d, jac, NULL, selpos, sel);
   mj_solveM2(m, d, jacM2, jac, sqrtInvD, 3);