Cannot substitute x with 0 in sin x

I tried this:

```
substitute [(x, 0)] (sin x)
```

Egison showed this error:

```
egison: Prelude.foldl1: empty list
```

`substitute' x 0 (sin x)` runs without error and returns `sin 0`. But when I tried to simplify the result using `mathNormalize`, it showed the same error again.