Fixed typo

src/build_system_wsmp.f90

@@ -192,7 +192,7 @@ do ileaves=1,osolve%nleaves
                   if (idof1 == 3) then
                     if (kfix((osolve%icon(k1,ileaves)-1)*ndof+idof1) < 1) then
                       iloc=ifind_loc_wsmp(i1loc,i1,ja,ia,n_iproc,nz_loc)
-                      elem_dz=(osolve%icon(5,ileaves)-osolve%icon(1,ileaves))*params%vex
+                      elem_dz=(osolve%z(osolve%icon(5,ileaves))-osolve%z(osolve%icon(1,ileaves)))*params%vex
                       if (k1 < 5) then                        
                         avals(iloc)=avals(iloc)-(params%dt*weightel(ileaves))/(2.d0*elem_dz)
                       else