Fix a loopy kerel error

meshmode/dof_array.py

@@ -195,7 +195,7 @@ def flatten(ary: np.ndarray) -> np.ndarray:
     def prg():
         return make_loopy_program(
             "{[iel,idof]: 0<=iel<nelements and 0<=idof<ndofs_per_element}",
-            "result[grp_start + iel*nunit_dofs + idof] = grp_ary[iel, idof]",
+            "result[grp_start + iel*ndofs_per_element + idof] = grp_ary[iel, idof]",  # noqa
             name="flatten")
 
     result = actx.empty(group_starts[-1], dtype=ary.entry_dtype)