ref - Ensure at-points operators skip cells with no points

Author: zatkins-dev

backends/ref/ceed-ref-operator.c

@@ -1054,6 +1054,7 @@ static int CeedOperatorApplyAddAtPoints_Ref(CeedOperator op, CeedVector in_vec,
     // Setup points for element
     CeedCallBackend(CeedElemRestrictionApplyAtPointsInElement(rstr_points, e, CEED_NOTRANSPOSE, point_coords, impl->point_coords_elem, request));
     CeedCallBackend(CeedElemRestrictionGetNumPointsInElement(rstr_points, e, &num_points));
+    if (num_points <= 0) continue;
 
     // Input basis apply
     CeedCallBackend(CeedOperatorInputBasisAtPoints_Ref(e, num_points_offset, num_points, qf_input_fields, op_input_fields, num_input_fields, in_vec,